In long-mode, bit 7 in the PDPTE is not reserved only if 1GB pages are
supported by the CPU. Currently the bit is considered by KVM as always
reserved.
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Now we can flush all the TLBs out of the mmu lock without TLB corruption when
write-proect the sptes, it is because:
- we have marked large sptes readonly instead of dropping them that means we
just change the spte from writable to readonly so that we only need to care
the case of changing spte from present to present (changing the spte from
present to nonpresent will flush all the TLBs immediately), in other words,
the only case we need to care is mmu_spte_update()
- in mmu_spte_update(), we haved checked
SPTE_HOST_WRITEABLE | PTE_MMU_WRITEABLE instead of PT_WRITABLE_MASK, that
means it does not depend on PT_WRITABLE_MASK anymore
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Relax the tlb flush condition since we will write-protect the spte out of mmu
lock. Note lockless write-protection only marks the writable spte to readonly
and the spte can be writable only if both SPTE_HOST_WRITEABLE and
SPTE_MMU_WRITEABLE are set (that are tested by spte_is_locklessly_modifiable)
This patch is used to avoid this kind of race:
VCPU 0 VCPU 1
lockless wirte protection:
set spte.w = 0
lock mmu-lock
write protection the spte to sync shadow page,
see spte.w = 0, then without flush tlb
unlock mmu-lock
!!! At this point, the shadow page can still be
writable due to the corrupt tlb entry
Flush all TLB
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Currently, kvm zaps the large spte if write-protected is needed, the later
read can fault on that spte. Actually, we can make the large spte readonly
instead of making them un-present, the page fault caused by read access can
be avoided
The idea is from Avi:
| As I mentioned before, write-protecting a large spte is a good idea,
| since it moves some work from protect-time to fault-time, so it reduces
| jitter. This removes the need for the return value.
This version has fixed the issue reported in 6b73a9606, the reason of that
issue is that fast_page_fault() directly sets the readonly large spte to
writable but only dirty the first page into the dirty-bitmap that means
other pages are missed. Fixed it by only the normal sptes (on the
PT_PAGE_TABLE_LEVEL level) can be fast fixed
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Using sp->role.level instead of @level since @level is not got from the
page table hierarchy
There is no issue in current code since the fast page fault currently only
fixes the fault caused by dirty-log that is always on the last level
(level = 1)
This patch makes the code more readable and avoids potential issue in the
further development
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
KVM does not handle the reserved bits of x86 page tables correctly:
In PAE, bits 5:8 are reserved in the PDPTE.
In IA-32e, bit 8 is not reserved.
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Rename variable smep to cr4_smep, which can better reflect the
meaning of the variable.
Signed-off-by: Feng Wu <feng.wu@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This patch adds SMAP handling logic when setting CR4 for guests
Thanks a lot to Paolo Bonzini for his suggestion to use the branchless
way to detect SMAP violation.
Signed-off-by: Feng Wu <feng.wu@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Read-only large sptes can be created due to read-only faults as
follows:
- QEMU pagetable entry that maps guest memory is read-only
due to COW.
- Guest read faults such memory, COW is not broken, because
it is a read-only fault.
- Enable dirty logging, large spte not nuked because it is read-only.
- Write-fault on such memory causes guest to loop endlessly
(which must go down to level 1 because dirty logging is enabled).
Fix by dropping large spte when necessary.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
By setting a Kconfig option, the architecture can control when
guest notifications will be presented by the apf backend.
There is the default batch mechanism, working as before, where the vcpu
thread should pull in this information.
Opposite to this, there is now the direct mechanism, that will push the
information to the guest.
This way s390 can use an already existing architecture interface.
Still the vcpu thread should call check_completion to cleanup leftovers.
Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
It is possible for __direct_map to be called on invalid root_hpa
(-1), two examples:
1) try_async_pf -> can_do_async_pf
-> vmx_interrupt_allowed -> nested_vmx_vmexit
2) vmx_handle_exit -> vmx_interrupt_allowed -> nested_vmx_vmexit
Then to load_vmcs12_host_state and kvm_mmu_reset_context.
Check for this possibility, let fault exception be regenerated.
BZ: https://bugzilla.redhat.com/show_bug.cgi?id=924916
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
kvm_mmu initialization is mostly filling in function pointers, there is
no way for it to fail. Clean up unused return values.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
They do the same thing, and destroy_kvm_mmu can be confused with
kvm_mmu_destroy.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
The new_cr3 MMU callback has been a wrapper for mmu_free_roots since commit
e676505 (KVM: MMU: Force cr3 reload with two dimensional paging on mov
cr3 emulation, 2012-07-08).
The commit message mentioned that "mmu_free_roots() is somewhat of an overkill,
but fixing that is more complicated and will be done after this minimal fix".
One year has passed, and no one really felt the need to do a different fix.
Wrap the call with a kvm_mmu_new_cr3 function for clarity, but remove the
callback.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
The free MMU callback has been a wrapper for mmu_free_roots since mmu_free_roots
itself was introduced (commit 17ac10a, [PATCH] KVM: MU: Special treatment
for shadow pae root pages, 2007-01-05), and has always been the same for all
MMU cases. Remove the indirection as it is useless.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
In commit e935b8372c ("KVM: Convert kvm_lock to raw_spinlock"),
the kvm_lock was made a raw lock. However, the kvm mmu_shrink()
function tries to grab the (non-raw) mmu_lock within the scope of
the raw locked kvm_lock being held. This leads to the following:
BUG: sleeping function called from invalid context at kernel/rtmutex.c:659
in_atomic(): 1, irqs_disabled(): 0, pid: 55, name: kswapd0
Preemption disabled at:[<ffffffffa0376eac>] mmu_shrink+0x5c/0x1b0 [kvm]
Pid: 55, comm: kswapd0 Not tainted 3.4.34_preempt-rt
Call Trace:
[<ffffffff8106f2ad>] __might_sleep+0xfd/0x160
[<ffffffff817d8d64>] rt_spin_lock+0x24/0x50
[<ffffffffa0376f3c>] mmu_shrink+0xec/0x1b0 [kvm]
[<ffffffff8111455d>] shrink_slab+0x17d/0x3a0
[<ffffffff81151f00>] ? mem_cgroup_iter+0x130/0x260
[<ffffffff8111824a>] balance_pgdat+0x54a/0x730
[<ffffffff8111fe47>] ? set_pgdat_percpu_threshold+0xa7/0xd0
[<ffffffff811185bf>] kswapd+0x18f/0x490
[<ffffffff81070961>] ? get_parent_ip+0x11/0x50
[<ffffffff81061970>] ? __init_waitqueue_head+0x50/0x50
[<ffffffff81118430>] ? balance_pgdat+0x730/0x730
[<ffffffff81060d2b>] kthread+0xdb/0xe0
[<ffffffff8106e122>] ? finish_task_switch+0x52/0x100
[<ffffffff817e1e94>] kernel_thread_helper+0x4/0x10
[<ffffffff81060c50>] ? __init_kthread_worker+0x
After the previous patch, kvm_lock need not be a raw spinlock anymore,
so change it back.
Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: kvm@vger.kernel.org
Cc: gleb@redhat.com
Cc: jan.kiszka@siemens.com
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Convert the remaining couple of random shrinkers in the tree to the new
API.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Glauber Costa <glommer@openvz.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: J. Bruce Fields <bfields@redhat.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Carlos Maiolino <cmaiolino@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Rientjes <rientjes@google.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: J. Bruce Fields <bfields@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
vcpu in page_fault_can_be_fast() is not used so remove it
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
If we let L1 use EPT, we should probably also support the INVEPT instruction.
In our current nested EPT implementation, when L1 changes its EPT table
for L2 (i.e., EPT12), L0 modifies the shadow EPT table (EPT02), and in
the course of this modification already calls INVEPT. But if last level
of shadow page is unsync not all L1's changes to EPT12 are intercepted,
which means roots need to be synced when L1 calls INVEPT. Global INVEPT
should not be different since roots are synced by kvm_mmu_load() each
time EPTP02 changes.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
KVM's existing shadow MMU code already supports nested TDP. To use it, we
need to set up a new "MMU context" for nested EPT, and create a few callbacks
for it (nested_ept_*()). This context should also use the EPT versions of
the page table access functions (defined in the previous patch).
Then, we need to switch back and forth between this nested context and the
regular MMU context when switching between L1 and L2 (when L1 runs this L2
with EPT).
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Inject nEPT fault to L1 guest. This patch is original from Xinhao.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
need_remote_flush() assumes that shadow page is in PT64 format, but
with addition of nested EPT this is no longer always true. Fix it by
bits definitions that depend on host shadow page type.
Reported-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Since nEPT doesn't support A/D bit, so we should not set those bit
when build shadow page table.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This is the first patch in a series which adds nested EPT support to KVM's
nested VMX. Nested EPT means emulating EPT for an L1 guest so that L1 can use
EPT when running a nested guest L2. When L1 uses EPT, it allows the L2 guest
to set its own cr3 and take its own page faults without either of L0 or L1
getting involved. This often significanlty improves L2's performance over the
previous two alternatives (shadow page tables over EPT, and shadow page
tables over shadow page tables).
This patch adds EPT support to paging_tmpl.h.
paging_tmpl.h contains the code for reading and writing page tables. The code
for 32-bit and 64-bit tables is very similar, but not identical, so
paging_tmpl.h is #include'd twice in mmu.c, once with PTTTYPE=32 and once
with PTTYPE=64, and this generates the two sets of similar functions.
There are subtle but important differences between the format of EPT tables
and that of ordinary x86 64-bit page tables, so for nested EPT we need a
third set of functions to read the guest EPT table and to write the shadow
EPT table.
So this patch adds third PTTYPE, PTTYPE_EPT, which creates functions (prefixed
with "EPT") which correctly read and write EPT tables.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
For preparation, we just move gpte_access(), prefetch_invalid_gpte(),
s_rsvd_bits_set(), protect_clean_gpte() and is_dirty_gpte() from mmu.c
to paging_tmpl.h.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Now that kvm_arch_memslots_updated() catches every increment of the
memslots->generation, checking if the mmio generation has reached its
maximum value is enough.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Currently, fast page fault incorrectly tries to fix mmio page fault when
the generation number is invalid (spte.gen != kvm.gen). It then returns
to guest to retry the fault since it sees the last spte is nonpresent.
This causes an infinite loop.
Since fast page fault only works for direct mmu, the issue exists when
1) tdp is enabled. It is only triggered only on AMD host since on Intel host
the mmio page fault is recognized as ept-misconfig whose handler call
fault-page path with error_code = 0
2) guest paging is disabled. Under this case, the issue is hardly discovered
since paging disable is short-lived and the sptes will be invalid after
memslot changed for 150 times
Fix it by filtering out MMIO page faults in page_fault_can_be_fast.
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Without this information, users will just see unexpected performance
problems and there is little chance we will get good reports from them:
note that mmio generation is increased even when we just start, or stop,
dirty logging for some memory slot, in which case users cannot expect
all shadow pages to be zapped.
printk_ratelimited() is used for this taking into account the problems
that we can see the information many times when we start multiple VMs
and guests can trigger this by reading ROM in a loop for example.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Document it to Documentation/virtual/kvm/mmu.txt
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop kvm_mmu_zap_mmio_sptes and use kvm_mmu_invalidate_zap_all_pages
instead to handle mmio generation number overflow
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Then it has the chance to trigger mmio generation number wrap-around
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
[Change from MMIO_MAX_GEN - 13 to MMIO_MAX_GEN - 150, because 13 is
very close to the number of calls to KVM_SET_USER_MEMORY_REGION
before the guest is started and there is any chance to create any
spte. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This patch tries to introduce a very simple and scale way to invalidate
all mmio sptes - it need not walk any shadow pages and hold mmu-lock
KVM maintains a global mmio valid generation-number which is stored in
kvm->memslots.generation and every mmio spte stores the current global
generation-number into his available bits when it is created
When KVM need zap all mmio sptes, it just simply increase the global
generation-number. When guests do mmio access, KVM intercepts a MMIO #PF
then it walks the shadow page table and get the mmio spte. If the
generation-number on the spte does not equal the global generation-number,
it will go to the normal #PF handler to update the mmio spte
Since 19 bits are used to store generation-number on mmio spte, we zap all
mmio sptes when the number is round
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Store the generation-number into bit3 ~ bit11 and bit52 ~ bit61, totally
19 bits can be used, it should be enough for nearly all most common cases
In this patch, the generation-number is always 0, it will be changed in
the later patch
[Gleb: masking generation bits from spte in get_mmio_spte_gfn() and
get_mmio_spte_access()]
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Quote Gleb's mail:
| why don't we check for sp->role.invalid in
| kvm_mmu_prepare_zap_page before calling kvm_reload_remote_mmus()?
and
| Actually we can add check for is_obsolete_sp() there too since
| kvm_mmu_invalidate_all_pages() already calls kvm_reload_remote_mmus()
| after incrementing mmu_valid_gen.
[ Xiao: add some comments and the check of is_obsolete_sp() ]
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
As Marcelo pointed out that
| "(retention of large number of pages while zapping)
| can be fatal, it can lead to OOM and host crash"
We introduce a list, kvm->arch.zapped_obsolete_pages, to link all
the pages which are deleted from the mmu cache but not actually
freed. When page reclaiming is needed, we always zap this kind of
pages first.
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
kvm_zap_obsolete_pages uses lock-break technique to zap pages,
it will flush tlb every time when it does lock-break
We can reload mmu on all vcpus after updating the generation
number so that the obsolete pages are not used on any vcpus,
after that we do not need to flush tlb when obsolete pages
are zapped
It will do kvm_mmu_prepare_zap_page many times and use one
kvm_mmu_commit_zap_page to collapse tlb flush, the side-effects
is that causes obsolete pages unlinked from active_list but leave
on hash-list, so we add the comment around the hash list walker
Note: kvm_mmu_commit_zap_page is still needed before free
the pages since other vcpus may be doing locklessly shadow
page walking
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Zap at lease 10 pages before releasing mmu-lock to reduce the overload
caused by requiring lock
After the patch, kvm_zap_obsolete_pages can forward progress anyway,
so update the comments
[ It improves the case 0.6% ~ 1% that do kernel building meanwhile read
PCI ROM. ]
Note: i am not sure that "10" is the best speculative value, i just
guessed that '10' can make vcpu do not spend long time on
kvm_zap_obsolete_pages and do not cause mmu-lock too hungry.
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
The obsolete page will be zapped soon, do not reuse it to
reduce future page fault
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
It is good for debug and development
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
The current kvm_mmu_zap_all is really slow - it is holding mmu-lock to
walk and zap all shadow pages one by one, also it need to zap all guest
page's rmap and all shadow page's parent spte list. Particularly, things
become worse if guest uses more memory or vcpus. It is not good for
scalability
In this patch, we introduce a faster way to invalidate all shadow pages.
KVM maintains a global mmu invalid generation-number which is stored in
kvm->arch.mmu_valid_gen and every shadow page stores the current global
generation-number into sp->mmu_valid_gen when it is created
When KVM need zap all shadow pages sptes, it just simply increase the
global generation-number then reload root shadow pages on all vcpus.
Vcpu will create a new shadow page table according to current kvm's
generation-number. It ensures the old pages are not used any more.
Then the obsolete pages (sp->mmu_valid_gen != kvm->arch.mmu_valid_gen)
are zapped by using lock-break technique
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Do locking around each case separately instead of having one lock and two
unlocks. Move root_hpa assignment out of the lock.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
No need to open-code this function.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
With the following commit, shadow pages can be zapped at random during
a shadow page talbe walk:
KVM: MMU: Move kvm_mmu_free_some_pages() into kvm_mmu_alloc_page()
7ddca7e43c
This patch reverts it and fixes __direct_map() and FNAME(fetch)().
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
The current name "kvm_mmu_free_some_pages" should be used for something
that actually frees some shadow pages, as we expect from the name, but
what the function is doing is to make some, KVM_MIN_FREE_MMU_PAGES,
shadow pages available: it does nothing when there are enough.
This patch changes the name to reflect this meaning better; while doing
this renaming, the code in the wrapper function is inlined into the main
body since the whole function will be inlined into the only caller now.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
What this function is doing is to ensure that the number of shadow pages
does not exceed the maximum limit stored in n_max_mmu_pages: so this is
placed at every code path that can reach kvm_mmu_alloc_page().
Although it might have some sense to spread this function in each such
code path when it could be called before taking mmu_lock, the rule was
changed not to do so.
Taking this background into account, this patch moves it into
kvm_mmu_alloc_page() and simplifies the code.
Note: the unlikely hint in kvm_mmu_free_some_pages() guarantees that the
overhead of this function is almost zero except when we actually need to
allocate some shadow pages, so we do not need to care about calling it
multiple times in one path by doing kvm_mmu_get_page() a few times.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
When we create or move a memory slot, we need to zap mmio sptes.
Currently, zap_all() is used for this and this is causing two problems:
- extra page faults after zapping mmu pages
- long mmu_lock hold time during zapping mmu pages
For the latter, Marcelo reported a disastrous mmu_lock hold time during
hot-plug, which made the guest unresponsive for a long time.
This patch takes a simple way to fix these problems: do not zap mmu
pages unless they are marked mmio cached. On our test box, this took
only 50us for the 4GB guest and we did not see ms of mmu_lock hold time
any more.
Note that we still need to do zap_all() for other cases. So another
work is also needed: Xiao's work may be the one.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This will be used not to zap unrelated mmu pages when creating/moving
a memory slot later.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Make the code for zapping the oldest mmu page, placed at the tail of the
active list, a separate function.
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
We are traversing the linked list, invalid_list, deleting each entry by
kvm_mmu_free_page(). _safe version is there for such a case.
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
The expression (sp)->gfn should not be expanded using @gfn.
Although no user of these macros passes a string other than gfn now,
this should be fixed before anyone sees strange errors.
Note: ignored the following checkpatch errors:
ERROR: Macros with complex values should be enclosed in parenthesis
ERROR: trailing statements should be on next line
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
I'm not sure why, but the hlist for each entry iterators were conceived
list_for_each_entry(pos, head, member)
The hlist ones were greedy and wanted an extra parameter:
hlist_for_each_entry(tpos, pos, head, member)
Why did they need an extra pos parameter? I'm not quite sure. Not only
they don't really need it, it also prevents the iterator from looking
exactly like the list iterator, which is unfortunate.
Besides the semantic patch, there was some manual work required:
- Fix up the actual hlist iterators in linux/list.h
- Fix up the declaration of other iterators based on the hlist ones.
- A very small amount of places were using the 'node' parameter, this
was modified to use 'obj->member' instead.
- Coccinelle didn't handle the hlist_for_each_entry_safe iterator
properly, so those had to be fixed up manually.
The semantic patch which is mostly the work of Peter Senna Tschudin is here:
@@
iterator name hlist_for_each_entry, hlist_for_each_entry_continue, hlist_for_each_entry_from, hlist_for_each_entry_rcu, hlist_for_each_entry_rcu_bh, hlist_for_each_entry_continue_rcu_bh, for_each_busy_worker, ax25_uid_for_each, ax25_for_each, inet_bind_bucket_for_each, sctp_for_each_hentry, sk_for_each, sk_for_each_rcu, sk_for_each_from, sk_for_each_safe, sk_for_each_bound, hlist_for_each_entry_safe, hlist_for_each_entry_continue_rcu, nr_neigh_for_each, nr_neigh_for_each_safe, nr_node_for_each, nr_node_for_each_safe, for_each_gfn_indirect_valid_sp, for_each_gfn_sp, for_each_host;
type T;
expression a,c,d,e;
identifier b;
statement S;
@@
-T b;
<+... when != b
(
hlist_for_each_entry(a,
- b,
c, d) S
|
hlist_for_each_entry_continue(a,
- b,
c) S
|
hlist_for_each_entry_from(a,
- b,
c) S
|
hlist_for_each_entry_rcu(a,
- b,
c, d) S
|
hlist_for_each_entry_rcu_bh(a,
- b,
c, d) S
|
hlist_for_each_entry_continue_rcu_bh(a,
- b,
c) S
|
for_each_busy_worker(a, c,
- b,
d) S
|
ax25_uid_for_each(a,
- b,
c) S
|
ax25_for_each(a,
- b,
c) S
|
inet_bind_bucket_for_each(a,
- b,
c) S
|
sctp_for_each_hentry(a,
- b,
c) S
|
sk_for_each(a,
- b,
c) S
|
sk_for_each_rcu(a,
- b,
c) S
|
sk_for_each_from
-(a, b)
+(a)
S
+ sk_for_each_from(a) S
|
sk_for_each_safe(a,
- b,
c, d) S
|
sk_for_each_bound(a,
- b,
c) S
|
hlist_for_each_entry_safe(a,
- b,
c, d, e) S
|
hlist_for_each_entry_continue_rcu(a,
- b,
c) S
|
nr_neigh_for_each(a,
- b,
c) S
|
nr_neigh_for_each_safe(a,
- b,
c, d) S
|
nr_node_for_each(a,
- b,
c) S
|
nr_node_for_each_safe(a,
- b,
c, d) S
|
- for_each_gfn_sp(a, c, d, b) S
+ for_each_gfn_sp(a, c, d) S
|
- for_each_gfn_indirect_valid_sp(a, c, d, b) S
+ for_each_gfn_indirect_valid_sp(a, c, d) S
|
for_each_host(a,
- b,
c) S
|
for_each_host_safe(a,
- b,
c, d) S
|
for_each_mesh_entry(a,
- b,
c, d) S
)
...+>
[akpm@linux-foundation.org: drop bogus change from net/ipv4/raw.c]
[akpm@linux-foundation.org: drop bogus hunk from net/ipv6/raw.c]
[akpm@linux-foundation.org: checkpatch fixes]
[akpm@linux-foundation.org: fix warnings]
[akpm@linux-foudnation.org: redo intrusive kvm changes]
Tested-by: Peter Senna Tschudin <peter.senna@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use link_shadow_page to link the sp to the spte in __direct_map
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
It is only used in debug code, so drop it
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Currently, kvm zaps the large spte if write-protected is needed, the later
read can fault on that spte. Actually, we can make the large spte readonly
instead of making them not present, the page fault caused by read access can
be avoided
The idea is from Avi:
| As I mentioned before, write-protecting a large spte is a good idea,
| since it moves some work from protect-time to fault-time, so it reduces
| jitter. This removes the need for the return value.
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This reverts commit bd4c86eaa6.
There is not user for kvm_mmu_isolate_page() any more.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Move base_role.nxe initialisation to where all other roles are initialized.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
spte_is_locklessly_modifiable() checks that both SPTE_HOST_WRITEABLE and
SPTE_MMU_WRITEABLE are present on spte. Make it more explicit.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
If the userspace starts dirty logging for a large slot, say 64GB of
memory, kvm_mmu_slot_remove_write_access() needs to hold mmu_lock for
a long time such as tens of milliseconds. This patch controls the lock
hold time by asking the scheduler if we need to reschedule for others.
One penalty for this is that we need to flush TLBs before releasing
mmu_lock. But since holding mmu_lock for a long time does affect not
only the guest, vCPU threads in other words, but also the host as a
whole, we should pay for that.
In practice, the cost will not be so high because we can protect a fair
amount of memory before being rescheduled: on my test environment,
cond_resched_lock() was called only once for protecting 12GB of memory
even without THP. We can also revisit Avi's "unlocked TLB flush" work
later for completely suppressing extra TLB flushes if needed.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Better to place mmu_lock handling and TLB flushing code together since
this is a self-contained function.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
No reason to make callers take mmu_lock since we do not need to protect
kvm_mmu_change_mmu_pages() and kvm_mmu_slot_remove_write_access()
together by mmu_lock in kvm_arch_commit_memory_region(): the former
calls kvm_mmu_commit_zap_page() and flushes TLBs by itself.
Note: we do not need to protect kvm->arch.n_requested_mmu_pages by
mmu_lock as can be seen from the fact that it is read locklessly.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This makes it possible to release mmu_lock and reschedule conditionally
in a later patch. Although this may increase the time needed to protect
the whole slot when we start dirty logging, the kernel should not allow
the userspace to trigger something that will hold a spinlock for such a
long time as tens of milliseconds: actually there is no limit since it
is roughly proportional to the number of guest pages.
Another point to note is that this patch removes the only user of
slot_bitmap which will cause some problems when we increase the number
of slots further.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
No longer need to care about the mapping level in this function.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
We have two issues in current code:
- if target gfn is used as its page table, guest will refault then kvm will use
small page size to map it. We need two #PF to fix its shadow page table
- sometimes, say a exception is triggered during vm-exit caused by #PF
(see handle_exception() in vmx.c), we remove all the shadow pages shadowed
by the target gfn before go into page fault path, it will cause infinite
loop:
delete shadow pages shadowed by the gfn -> try to use large page size to map
the gfn -> retry the access ->...
To fix these, we can adjust page size early if the target gfn is used as page
table
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
If the write-fault access is from supervisor and CR0.WP is not set on the
vcpu, kvm will fix it by adjusting pte access - it sets the W bit on pte
and clears U bit. This is the chance that kvm can change pte access from
readonly to writable
Unfortunately, the pte access is the access of 'direct' shadow page table,
means direct sp.role.access = pte_access, then we will create a writable
spte entry on the readonly shadow page table. It will cause Dirty bit is
not tracked when two guest ptes point to the same large page. Note, it
does not have other impact except Dirty bit since cr0.wp is encoded into
sp.role
It can be fixed by adjusting pte access before establishing shadow page
table. Also, after that, no mmu specified code exists in the common function
and drop two parameters in set_spte
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
There are two cases we need to adjust page size in set_spte:
1): the one is other vcpu creates new sp in the window between mapping_level()
and acquiring mmu-lock.
2): the another case is the new sp is created by itself (page-fault path) when
guest uses the target gfn as its page table.
In current code, set_spte drop the spte and emulate the access for these case,
it works not good:
- for the case 1, it may destroy the mapping established by other vcpu, and
do expensive instruction emulation.
- for the case 2, it may emulate the access even if the guest is accessing
the page which not used as page table. There is a example, 0~2M is used as
huge page in guest, in this huge page, only page 3 used as page table, then
guest read/writes on other pages can cause instruction emulation.
Both of these cases can be fixed by allowing guest to retry the access, it
will refault, then we can establish the mapping by using small page
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This patch filters noslot pfn out from error pfns based on Marcelo comment:
noslot pfn is not a error pfn
After this patch,
- is_noslot_pfn indicates that the gfn is not in slot
- is_error_pfn indicates that the gfn is in slot but the error is occurred
when translate the gfn to pfn
- is_error_noslot_pfn indicates that the pfn either it is error pfns or it
is noslot pfn
And is_invalid_pfn can be removed, it makes the code more clean
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Merge reason: development work has dependency on kvm patches merged
upstream.
Conflicts:
arch/powerpc/include/asm/Kbuild
arch/powerpc/include/asm/kvm_para.h
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
The mmu_notifier_retry is not specific to any vcpu (and never will be)
so only take struct kvm as a parameter.
The motivation is the ARM mmu code that needs to call this from
somewhere where we long let go of the vcpu pointer.
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
We can not directly call kvm_release_pfn_clean to release the pfn
since we can meet noslot pfn which is used to cache mmio info into
spte
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>
The function does not depend on guest mmu mode, move it out from
paging_tmpl.h
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Remove mmu_is_invalid and use is_invalid_pfn instead
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Instead of branchy code depending on level, gpte.ps, and mmu configuration,
prepare everything in a bitmap during mode changes and look it up during
runtime.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
walk_addr_generic() permission checks are a maze of branchy code, which is
performed four times per lookup. It depends on the type of access, efer.nxe,
cr0.wp, cr4.smep, and in the near future, cr4.smap.
Optimize this away by precalculating all variants and storing them in a
bitmap. The bitmap is recalculated when rarely-changing variables change
(cr0, cr4) and is indexed by the often-changing variables (page fault error
code, pte access permissions).
The permission check is moved to the end of the loop, otherwise an SMEP
fault could be reported as a false positive, when PDE.U=1 but PTE.U=0.
Noted by Xiao Guangrong.
The result is short, branch-free code.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
We no longer rely on paging_tmpl.h defines; so we can move the function
to mmu.c.
Rely on zero extension to 64 bits to get the correct nx behaviour.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
gpte_access() computes the access permissions of a guest pte and also
write-protects clean gptes. This is wrong when we are servicing a
write fault (since we'll be setting the dirty bit momentarily) but
correct when instantiating a speculative spte, or when servicing a
read fault (since we'll want to trap a following write in order to
set the dirty bit).
It doesn't seem to hurt in practice, but in order to make the code
readable, push the write protection out of gpte_access() and into
a new protect_clean_gpte() which is called explicitly when needed.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Checking the return of kvm_mmu_get_page is unnecessary since it is
guaranteed by memory cache
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Merging critical fixes from upstream required for development.
* upstream/master: (809 commits)
libata: Add a space to " 2GB ATA Flash Disk" DMA blacklist entry
Revert "powerpc: Update g5_defconfig"
powerpc/perf: Use pmc_overflow() to detect rolled back events
powerpc: Fix VMX in interrupt check in POWER7 copy loops
powerpc: POWER7 copy_to_user/copy_from_user patch applied twice
powerpc: Fix personality handling in ppc64_personality()
powerpc/dma-iommu: Fix IOMMU window check
powerpc: Remove unnecessary ifdefs
powerpc/kgdb: Restore current_thread_info properly
powerpc/kgdb: Bail out of KGDB when we've been triggered
powerpc/kgdb: Do not set kgdb_single_step on ppc
powerpc/mpic_msgr: Add missing includes
powerpc: Fix null pointer deref in perf hardware breakpoints
powerpc: Fixup whitespace in xmon
powerpc: Fix xmon dl command for new printk implementation
xfs: check for possible overflow in xfs_ioc_trim
xfs: unlock the AGI buffer when looping in xfs_dialloc
xfs: fix uninitialised variable in xfs_rtbuf_get()
powerpc/fsl: fix "Failed to mount /dev: No such device" errors
powerpc/fsl: update defconfigs
...
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Although the possible race described in
commit 85b7059169
KVM: MMU: fix shrinking page from the empty mmu
was correct, the real cause of that issue was a more trivial bug of
mmu_shrink() introduced by
commit 1952639665
KVM: MMU: do not iterate over all VMs in mmu_shrink()
Here is the bug:
if (kvm->arch.n_used_mmu_pages > 0) {
if (!nr_to_scan--)
break;
continue;
}
We skip VMs whose n_used_mmu_pages is not zero and try to shrink others:
in other words we try to shrink empty ones by mistake.
This patch reverses the logic so that mmu_shrink() can free pages from
the first VM whose n_used_mmu_pages is not zero. Note that we also add
comments explaining the role of nr_to_scan which is not practically
important now, hoping this will be improved in the future.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
In current code, if we map a readonly memory space from host to guest
and the page is not currently mapped in the host, we will get a fault
pfn and async is not allowed, then the vm will crash
We introduce readonly memory region to map ROM/ROMD to the guest, read access
is happy for readonly memslot, write access on readonly memslot will cause
KVM_EXIT_MMIO exit
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
After commit a2766325cf, the error pfn is replaced by the
error code, it need not be released anymore
[ The patch has been compiling tested for powerpc ]
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Then, get_hwpoison_pfn and is_hwpoison_pfn can be removed
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
After that, the exported and un-inline function, get_fault_pfn,
can be removed
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Two reasons:
- x86 can integrate rmap and rmap_pde and remove heuristics in
__gfn_to_rmap().
- Some architectures do not need rmap.
Since rmap is one of the most memory consuming stuff in KVM, ppc'd
better restrict the allocation to Book3S HV.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Avi Kivity <avi@redhat.com>
This helps to make rmap architecture specific in a later patch.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
The current code depends on the fact that fault_page is the normal page,
however, we will use the error code instead of these dummy pages in the
later patch, so we use kvm_release_pfn_clean to release pfn which will
release the error code properly
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Merge patches queued during the run-up to the merge window.
* queue: (25 commits)
KVM: Choose better candidate for directed yield
KVM: Note down when cpu relax intercepted or pause loop exited
KVM: Add config to support ple or cpu relax optimzation
KVM: switch to symbolic name for irq_states size
KVM: x86: Fix typos in pmu.c
KVM: x86: Fix typos in lapic.c
KVM: x86: Fix typos in cpuid.c
KVM: x86: Fix typos in emulate.c
KVM: x86: Fix typos in x86.c
KVM: SVM: Fix typos
KVM: VMX: Fix typos
KVM: remove the unused parameter of gfn_to_pfn_memslot
KVM: remove is_error_hpa
KVM: make bad_pfn static to kvm_main.c
KVM: using get_fault_pfn to get the fault pfn
KVM: MMU: track the refcount when unmap the page
KVM: x86: remove unnecessary mark_page_dirty
KVM: MMU: Avoid handling same rmap_pde in kvm_handle_hva_range()
KVM: MMU: Push trace_kvm_age_page() into kvm_age_rmapp()
KVM: MMU: Add memslot parameter to hva handlers
...
Signed-off-by: Avi Kivity <avi@redhat.com>
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Merge tag 'kvm-3.6-1' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull KVM updates from Avi Kivity:
"Highlights include
- full big real mode emulation on pre-Westmere Intel hosts (can be
disabled with emulate_invalid_guest_state=0)
- relatively small ppc and s390 updates
- PCID/INVPCID support in guests
- EOI avoidance; 3.6 guests should perform better on 3.6 hosts on
interrupt intensive workloads)
- Lockless write faults during live migration
- EPT accessed/dirty bits support for new Intel processors"
Fix up conflicts in:
- Documentation/virtual/kvm/api.txt:
Stupid subchapter numbering, added next to each other.
- arch/powerpc/kvm/booke_interrupts.S:
PPC asm changes clashing with the KVM fixes
- arch/s390/include/asm/sigp.h, arch/s390/kvm/sigp.c:
Duplicated commits through the kvm tree and the s390 tree, with
subsequent edits in the KVM tree.
* tag 'kvm-3.6-1' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (93 commits)
KVM: fix race with level interrupts
x86, hyper: fix build with !CONFIG_KVM_GUEST
Revert "apic: fix kvm build on UP without IOAPIC"
KVM guest: switch to apic_set_eoi_write, apic_write
apic: add apic_set_eoi_write for PV use
KVM: VMX: Implement PCID/INVPCID for guests with EPT
KVM: Add x86_hyper_kvm to complete detect_hypervisor_platform check
KVM: PPC: Critical interrupt emulation support
KVM: PPC: e500mc: Fix tlbilx emulation for 64-bit guests
KVM: PPC64: booke: Set interrupt computation mode for 64-bit host
KVM: PPC: bookehv: Add ESR flag to Data Storage Interrupt
KVM: PPC: bookehv64: Add support for std/ld emulation.
booke: Added crit/mc exception handler for e500v2
booke/bookehv: Add host crit-watchdog exception support
KVM: MMU: document mmu-lock and fast page fault
KVM: MMU: fix kvm_mmu_pagetable_walk tracepoint
KVM: MMU: trace fast page fault
KVM: MMU: fast path of handling guest page fault
KVM: MMU: introduce SPTE_MMU_WRITEABLE bit
KVM: MMU: fold tlb flush judgement into mmu_spte_update
...
The parameter, 'kvm', is not used in gfn_to_pfn_memslot, we can happily remove
it
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Using get_fault_pfn to cleanup the code
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
It will trigger a WARN_ON if the page has been freed but it is still
used in mmu, it can help us to detect mm bug early
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
When we invalidate a THP page, we call the handler with the same
rmap_pde argument 512 times in the following loop:
for each guest page in the range
for each level
unmap using rmap
This patch avoids these extra handler calls by changing the loop order
like this:
for each level
for each rmap in the range
unmap using rmap
With the preceding patches in the patch series, this made THP page
invalidation more than 5 times faster on our x86 host: the host became
more responsive during swapping the guest's memory as a result.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This restricts the tracing to page aging and makes it possible to
optimize kvm_handle_hva_range() further in the following patch.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This is needed to push trace_kvm_age_page() into kvm_age_rmapp() in the
following patch.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This makes it possible to loop over rmap_pde arrays in the same way as
we do over rmap so that we can optimize kvm_handle_hva_range() easily in
the following patch.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
When we tested KVM under memory pressure, with THP enabled on the host,
we noticed that MMU notifier took a long time to invalidate huge pages.
Since the invalidation was done with mmu_lock held, it not only wasted
the CPU but also made the host harder to respond.
This patch mitigates this by using kvm_handle_hva_range().
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: Alexander Graf <agraf@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
When guest's memory is backed by THP pages, MMU notifier needs to call
kvm_unmap_hva(), which in turn leads to kvm_handle_hva(), in a loop to
invalidate a range of pages which constitute one huge page:
for each page
for each memslot
if page is in memslot
unmap using rmap
This means although every page in that range is expected to be found in
the same memslot, we are forced to check unrelated memslots many times.
If the guest has more memslots, the situation will become worse.
Furthermore, if the range does not include any pages in the guest's
memory, the loop over the pages will just consume extra time.
This patch, together with the following patches, solves this problem by
introducing kvm_handle_hva_range() which makes the loop look like this:
for each memslot
for each page in memslot
unmap using rmap
In this new processing, the actual work is converted to a loop over rmap
which is much more cache friendly than before.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: Alexander Graf <agraf@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This restricts hva handling in mmu code and makes it easier to extend
kvm_handle_hva() so that it can treat a range of addresses later in this
patch series.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: Alexander Graf <agraf@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
We can treat every level uniformly.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
To see what happen on this path and help us to optimize it
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
If the the present bit of page fault error code is set, it indicates
the shadow page is populated on all levels, it means what we do is
only modify the access bit which can be done out of mmu-lock
Currently, in order to simplify the code, we only fix the page fault
caused by write-protect on the fast path
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This bit indicates whether the spte can be writable on MMU, that means
the corresponding gpte is writable and the corresponding gfn is not
protected by shadow page protection
In the later path, SPTE_MMU_WRITEABLE will indicates whether the spte
can be locklessly updated
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
mmu_spte_update() is the common function, we can easily audit the path
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Use __drop_large_spte to cleanup this function and comment spte_write_protect
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Introduce a common function to abstract spte write-protect to
cleanup the code
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
The reture value of __rmap_write_protect is either 1 or 0, use
true/false instead of these
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Currently the MMU's ->new_cr3() callback does nothing when guest paging
is disabled or when two-dimentional paging (e.g. EPT on Intel) is active.
This means that an emulated write to cr3 can be lost; kvm_set_cr3() will
write vcpu-arch.cr3, but the GUEST_CR3 field in the VMCS will retain its
old value and this is what the guest sees.
This bug did not have any effect until now because:
- with unrestricted guest, or with svm, we never emulate a mov cr3 instruction
- without unrestricted guest, and with paging enabled, we also never emulate a
mov cr3 instruction
- without unrestricted guest, but with paging disabled, the guest's cr3 is
ignored until the guest enables paging; at this point the value from arch.cr3
is loaded correctly my the mov cr0 instruction which turns on paging
However, the patchset that enables big real mode causes us to emulate mov cr3
instructions in protected mode sometimes (when guest state is not virtualizable
by vmx); this mov cr3 is effectively ignored and will crash the guest.
The fix is to make nonpaging_new_cr3() call mmu_free_roots() to force a cr3
reload. This is awkward because now all the new_cr3 callbacks to the same
thing, and because mmu_free_roots() is somewhat of an overkill; but fixing
that is more complicated and will be done after this minimal fix.
Observed in the Window XP 32-bit installer while bringing up secondary vcpus.
Signed-off-by: Avi Kivity <avi@redhat.com>
EPT Dirty bit use bit 9 as Intel SDM definition, to avoid conflict, change
PT_FIRST_AVAIL_BITS_SHIFT to 10.
Signed-off-by: Xudong Hao <xudong.hao@intel.com>
Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Size is not needed to return one from pre-allocated objects.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
I see this in 3.5-rc1:
arch/x86/kvm/mmu.c: In function ‘kvm_test_age_rmapp’:
arch/x86/kvm/mmu.c:1271: warning: ‘iter.desc’ may be used uninitialized in this function
The line in question was introduced by commit
1e3f42f03c
static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
unsigned long data)
{
- u64 *spte;
+ u64 *sptep;
+ struct rmap_iterator iter; <- line 1271
int young = 0;
/*
The reason I think is that the compiler assumes that
the rmap value could be 0, so
static u64 *rmap_get_first(unsigned long rmap, struct rmap_iterator
*iter)
{
if (!rmap)
return NULL;
if (!(rmap & 1)) {
iter->desc = NULL;
return (u64 *)rmap;
}
iter->desc = (struct pte_list_desc *)(rmap & ~1ul);
iter->pos = 0;
return iter->desc->sptes[iter->pos];
}
will not initialize iter.desc, but the compiler isn't
smart enough to see that
for (sptep = rmap_get_first(*rmapp, &iter); sptep;
sptep = rmap_get_next(&iter)) {
will immediately exit in this case.
I checked by adding
if (!*rmapp)
goto out;
on top which is clearly equivalent but disables the warning.
This patch uses uninitialized_var to disable the warning without
increasing code size.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
mmu_shrink() needlessly iterates over all VMs even though it will not
attempt to free mmu pages from more than one on them. Fix that and also
check used mmu pages count outside of VM lock to skip inactive VMs faster.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
The huge page size is 4M on non-PAE host, but 2M page size is used in
transparent_hugepage_adjust(), so the page we get after adjust the
mapping level is not the head page, the BUG_ON() will be triggered
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Using RCU for lockless shadow walking can increase the amount of memory
in use by the system, since RCU grace periods are unpredictable. We also
have an unconditional write to a shared variable (reader_counter), which
isn't good for scaling.
Replace that with a scheme similar to x86's get_user_pages_fast(): disable
interrupts during lockless shadow walk to force the freer
(kvm_mmu_commit_zap_page()) to wait for the TLB flush IPI to find the
processor with interrupts enabled.
We also add a new vcpu->mode, READING_SHADOW_PAGE_TABLES, to prevent
kvm_flush_remote_tlbs() from avoiding the IPI.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Its much cleaner to use PT_PAGE_TABLE_LEVEL than its numeric value.
Signed-off-by: Davidlohr Bueso <dave@gnu.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Iteration using rmap_next(), the actual body is pte_list_next(), is
inefficient: every time we call it we start from checking whether rmap
holds a single spte or points to a descriptor which links more sptes.
In the case of shadow paging, this quadratic total iteration cost is a
problem. Even for two dimensional paging, with EPT/NPT on, in which we
almost always have a single mapping, the extra checks at the end of the
iteration should be eliminated.
This patch fixes this by introducing rmap_iterator which keeps the
iteration context for the next search. Furthermore the implementation
of rmap_next() is splitted into two functions, rmap_get_first() and
rmap_get_next(), to avoid repeatedly checking whether the rmap being
iterated on has only one spte.
Although there seemed to be only a slight change for EPT/NPT, the actual
improvement was significant: we observed that GET_DIRTY_LOG for 1GB
dirty memory became 15% faster than before. This is probably because
the new code is easy to make branch predictions.
Note: we just remove pte_list_next() because we can think of parent_ptes
as a reverse mapping.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
We have PTE_LIST_EXT + 1 pointers in this structure and these 40/20
bytes do not fit cache lines well. Furthermore, some allocators may
use 64/32-byte objects for the pte_list_desc cache.
This patch solves this problem by changing PTE_LIST_EXT from 4 to 3.
For shadow paging, the new size is still large enough to hold both the
kernel and process mappings for usual anonymous pages. For file
mappings, there may be a slight change in the cache usage.
Note: with EPT/NPT we almost always have a single spte in each reverse
mapping and we will not see any change by this.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
Dropped such mappings when we enabled dirty logging and we will never
create new ones until we stop the logging.
For this we introduce a new function which can be used to write protect
a range of PT level pages: although we do not need to care about a range
of pages at this point, the following patch will need this feature to
optimize the write protection of many pages.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
We will use this in the following patch to implement another function
which needs to write protect pages using the rmap information.
Note that there is a small change in debug printing for large pages:
we do not differentiate them from others to avoid duplicating code.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
The reset_rsvds_bits_mask() function can use the guest walker's root level
number instead of using a separate 'level' variable.
Signed-off-by: Davidlohr Bueso <dave@gnu.org>
Signed-off-by: Avi Kivity <avi@redhat.com>
Some members of kvm_memory_slot are not used by every architecture.
This patch is the first step to make this difference clear by
introducing kvm_memory_slot::arch; lpage_info is moved into it.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This patch cleans up the code and removes the "(void)level;" warning
suppressor.
Note that we can also use this for PT_PAGE_TABLE_LEVEL to treat every
level uniformly later.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
We can remove the first ->nx state assignment since it is assigned afterwards anyways.
Signed-off-by: Davidlohr Bueso <dave@gnu.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
get_written_sptes is called twice in kvm_mmu_pte_write, one of them can be
removed
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
There is only one user of it and for_each_set_bit() does the same.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
module_param(bool) used to counter-intuitively take an int. In
fddd5201 (mid-2009) we allowed bool or int/unsigned int using a messy
trick.
It's time to remove the int/unsigned int option. For this version
it'll simply give a warning, but it'll break next kernel version.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
freed_pages is never evaluated, so remove it as well as the return code
kvm_mmu_remove_some_alloc_mmu_pages so far delivered to its only user.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
The unsync code should be stable now, maybe it is the time to remove this
parameter to cleanup the code a little bit
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Move the mmu code in kvm_arch_vcpu_init() to kvm_mmu_create()
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
The tracepoint is only used to audit mmu code, it should not be exposed to
user, let us replace it with jump-label.
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Introduce kvm_for_each_memslot to walk all valid memslot
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Currently, write protecting a slot needs to walk all the shadow pages
and checks ones which have a pte mapping a page in it.
The walk is overly heavy when dirty pages in that slot are not so many
and checking the shadow pages would result in unwanted cache pollution.
To mitigate this problem, we use rmap_write_protect() and check only
the sptes which can be reached from gfns marked in the dirty bitmap
when the number of dirty pages are less than that of shadow pages.
This criterion is reasonable in its meaning and worked well in our test:
write protection became some times faster than before when the ratio of
dirty pages are low and was not worse even when the ratio was near the
criterion.
Note that the locking for this write protection becomes fine grained.
The reason why this is safe is descripted in the comments.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
rmap_write_protect() calls gfn_to_rmap() for each level with gfn fixed.
This results in calling gfn_to_memslot() repeatedly with that gfn.
This patch introduces __gfn_to_rmap() which takes the slot as an
argument to avoid this.
This is also needed for the following dirty logging optimization.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
Nadav Amit