Commit Graph

2090 Commits

Author SHA1 Message Date
Joerg Roedel 1018faa6cf perf/x86/kvm: Fix Host-Only/Guest-Only counting with SVM disabled
It turned out that a performance counter on AMD does not
count at all when the GO or HO bit is set in the control
register and SVM is disabled in EFER.

This patch works around this issue by masking out the HO bit
in the performance counter control register when SVM is not
enabled.

The GO bit is not touched because it is only set when the
user wants to count in guest-mode only. So when SVM is
disabled the counter should not run at all and the
not-counting is the intended behaviour.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Avi Kivity <avi@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: stable@vger.kernel.org # v3.2
Link: http://lkml.kernel.org/r/1330523852-19566-1-git-send-email-joerg.roedel@amd.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-02 12:16:39 +01:00
Linus Torvalds f94edacf99 i387: move TS_USEDFPU flag from thread_info to task_struct
This moves the bit that indicates whether a thread has ownership of the
FPU from the TS_USEDFPU bit in thread_info->status to a word of its own
(called 'has_fpu') in task_struct->thread.has_fpu.

This fixes two independent bugs at the same time:

 - changing 'thread_info->status' from the scheduler causes nasty
   problems for the other users of that variable, since it is defined to
   be thread-synchronous (that's what the "TS_" part of the naming was
   supposed to indicate).

   So perfectly valid code could (and did) do

	ti->status |= TS_RESTORE_SIGMASK;

   and the compiler was free to do that as separate load, or and store
   instructions.  Which can cause problems with preemption, since a task
   switch could happen in between, and change the TS_USEDFPU bit. The
   change to TS_USEDFPU would be overwritten by the final store.

   In practice, this seldom happened, though, because the 'status' field
   was seldom used more than once, so gcc would generally tend to
   generate code that used a read-modify-write instruction and thus
   happened to avoid this problem - RMW instructions are naturally low
   fat and preemption-safe.

 - On x86-32, the current_thread_info() pointer would, during interrupts
   and softirqs, point to a *copy* of the real thread_info, because
   x86-32 uses %esp to calculate the thread_info address, and thus the
   separate irq (and softirq) stacks would cause these kinds of odd
   thread_info copy aliases.

   This is normally not a problem, since interrupts aren't supposed to
   look at thread information anyway (what thread is running at
   interrupt time really isn't very well-defined), but it confused the
   heck out of irq_fpu_usable() and the code that tried to squirrel
   away the FPU state.

   (It also caused untold confusion for us poor kernel developers).

It also turns out that using 'task_struct' is actually much more natural
for most of the call sites that care about the FPU state, since they
tend to work with the task struct for other reasons anyway (ie
scheduling).  And the FPU data that we are going to save/restore is
found there too.

Thanks to Arjan Van De Ven <arjan@linux.intel.com> for pointing us to
the %esp issue.

Cc: Arjan van de Ven <arjan@linux.intel.com>
Reported-and-tested-by: Raphael Prevost <raphael@buro.asia>
Acked-and-tested-by: Suresh Siddha <suresh.b.siddha@intel.com>
Tested-by: Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-02-18 10:19:41 -08:00
Linus Torvalds 6d59d7a9f5 i387: don't ever touch TS_USEDFPU directly, use helper functions
This creates three helper functions that do the TS_USEDFPU accesses, and
makes everybody that used to do it by hand use those helpers instead.

In addition, there's a couple of helper functions for the "change both
CR0.TS and TS_USEDFPU at the same time" case, and the places that do
that together have been changed to use those.  That means that we have
fewer random places that open-code this situation.

The intent is partly to clarify the code without actually changing any
semantics yet (since we clearly still have some hard to reproduce bug in
this area), but also to make it much easier to use another approach
entirely to caching the CR0.TS bit for software accesses.

Right now we use a bit in the thread-info 'status' variable (this patch
does not change that), but we might want to make it a full field of its
own or even make it a per-cpu variable.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-02-16 13:33:12 -08:00
Gleb Natapov 5753785fa9 KVM: do not #GP on perf MSR writes when vPMU is disabled
Return to behaviour perf MSR had before introducing vPMU in case vPMU
is disabled. Some guests access those registers unconditionally and do
not expect it to fail.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2012-02-01 11:44:46 +02:00
Stephan Bärwolf c2226fc9e8 KVM: x86: fix missing checks in syscall emulation
On hosts without this patch, 32bit guests will crash (and 64bit guests
may behave in a wrong way) for example by simply executing following
nasm-demo-application:

    [bits 32]
    global _start
    SECTION .text
    _start: syscall

(I tested it with winxp and linux - both always crashed)

    Disassembly of section .text:

    00000000 <_start>:
       0:   0f 05                   syscall

The reason seems a missing "invalid opcode"-trap (int6) for the
syscall opcode "0f05", which is not available on Intel CPUs
within non-longmodes, as also on some AMD CPUs within legacy-mode.
(depending on CPU vendor, MSR_EFER and cpuid)

Because previous mentioned OSs may not engage corresponding
syscall target-registers (STAR, LSTAR, CSTAR), they remain
NULL and (non trapping) syscalls are leading to multiple
faults and finally crashs.

Depending on the architecture (AMD or Intel) pretended by
guests, various checks according to vendor's documentation
are implemented to overcome the current issue and behave
like the CPUs physical counterparts.

[mtosatti: cleanup/beautify code]

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2012-02-01 11:43:40 +02:00
Stephan Bärwolf bdb42f5afe KVM: x86: extend "struct x86_emulate_ops" with "get_cpuid"
In order to be able to proceed checks on CPU-specific properties
within the emulator, function "get_cpuid" is introduced.
With "get_cpuid" it is possible to virtually call the guests
"cpuid"-opcode without changing the VM's context.

[mtosatti: cleanup/beautify code]

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2012-02-01 11:43:33 +02:00
Rusty Russell 476bc0015b module_param: make bool parameters really bool (arch)
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>
2012-01-13 09:32:18 +10:30
Avi Kivity 222d21aa07 KVM: x86 emulator: implement RDPMC (0F 33)
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:24:43 +02:00
Avi Kivity 80bdec64c0 KVM: x86 emulator: fix RDPMC privilege check
RDPMC is only privileged if CR4.PCE=0.  check_rdpmc() already implements this,
so all we need to do is drop the Priv flag.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:24:41 +02:00
Gleb Natapov a6c06ed1a6 KVM: Expose the architectural performance monitoring CPUID leaf
Provide a CPUID leaf that describes the emulated PMU.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:24:40 +02:00
Avi Kivity fee84b079d KVM: VMX: Intercept RDPMC
Intercept RDPMC and forward it to the PMU emulation code.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:24:38 +02:00
Avi Kivity 332b56e484 KVM: SVM: Intercept RDPMC
Intercept RDPMC and forward it to the PMU emulation code.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:24:37 +02:00
Avi Kivity 022cd0e840 KVM: Add generic RDPMC support
Add a helper function that emulates the RDPMC instruction operation.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:24:35 +02:00
Gleb Natapov f5132b0138 KVM: Expose a version 2 architectural PMU to a guests
Use perf_events to emulate an architectural PMU, version 2.

Based on PMU version 1 emulation by Avi Kivity.

[avi: adjust for cpuid.c]
[jan: fix anonymous field initialization for older gcc]

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:24:29 +02:00
Avi Kivity 8934208221 KVM: Expose kvm_lapic_local_deliver()
Needed to deliver performance monitoring interrupts.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:23:39 +02:00
Takuya Yoshikawa e0dac408d0 KVM: x86 emulator: Use opcode::execute for Group 9 instruction
Group 9: 0F C7

Rename em_grp9() to em_cmpxchg8b() and register it.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:23:38 +02:00
Takuya Yoshikawa c04ec8393f KVM: x86 emulator: Use opcode::execute for Group 4/5 instructions
Group 4: FE
Group 5: FF

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:23:36 +02:00
Takuya Yoshikawa c15af35f54 KVM: x86 emulator: Use opcode::execute for Group 1A instruction
Group 1A: 8F

Register em_pop() directly and remove em_grp1a().

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:23:35 +02:00
Gleb Natapov d546cb406e KVM: drop bsp_vcpu pointer from kvm struct
Drop bsp_vcpu pointer from kvm struct since its only use is incorrect
anyway.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:22:32 +02:00
Jan Kiszka a647795efb KVM: x86: Consolidate PIT legacy test
Move the test for KVM_PIT_FLAGS_HPET_LEGACY into create_pit_timer
instead of replicating it on the caller site.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:22:30 +02:00
Jan Kiszka bb5a798ad5 KVM: x86: Do not rely on implicit inclusions
Works so far by change, but it is not guaranteed to stay like this.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:22:29 +02:00
Avi Kivity 43771ebfc9 KVM: Make KVM_INTEL depend on CPU_SUP_INTEL
PMU virtualization needs to talk to Intel-specific bits of perf; these are
only available when CPU_SUP_INTEL=y.

Fixes

  arch/x86/built-in.o: In function `atomic_switch_perf_msrs':
  vmx.c:(.text+0x6b1d4): undefined reference to `perf_guest_get_msrs'

Reported-by: Ingo Molnar <mingo@elte.hu>
Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:22:27 +02:00
Sasha Levin ff5c2c0316 KVM: Use memdup_user instead of kmalloc/copy_from_user
Switch to using memdup_user when possible. This makes code more
smaller and compact, and prevents errors.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:22:21 +02:00
Sasha Levin cdfca7b346 KVM: Use kmemdup() instead of kmalloc/memcpy
Switch to kmemdup() in two places to shorten the code and avoid possible bugs.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:22:20 +02:00
Jan Kiszka 234b639206 KVM: x86 emulator: Remove set-but-unused cr4 from check_cr_write
This was probably copy&pasted from the cr0 case, but it's unneeded here.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:22:16 +02:00
Jan Kiszka 3d56cbdf35 KVM: MMU: Drop unused return value of kvm_mmu_remove_some_alloc_mmu_pages
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>
2011-12-27 11:22:15 +02:00
Alex,Shi 086c985501 KVM: use this_cpu_xxx replace percpu_xxx funcs
percpu_xxx funcs are duplicated with this_cpu_xxx funcs, so replace them
for further code clean up.

And in preempt safe scenario, __this_cpu_xxx funcs has a bit better
performance since __this_cpu_xxx has no redundant preempt_disable()

Signed-off-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:22:13 +02:00
Xiao Guangrong e37fa7853c KVM: MMU: audit: inline audit function
inline audit function and little cleanup

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:22:12 +02:00
Xiao Guangrong d750ea2886 KVM: MMU: remove oos_shadow parameter
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>
2011-12-27 11:22:10 +02:00
Xiao Guangrong e459e3228d KVM: MMU: move the relevant mmu code to mmu.c
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>
2011-12-27 11:22:09 +02:00
Xiao Guangrong 9edb17d55f KVM: x86: remove the dead code of KVM_EXIT_HYPERCALL
KVM_EXIT_HYPERCALL is not used anymore, so remove the code

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:22:07 +02:00
Xiao Guangrong 0375f7fad9 KVM: MMU: audit: replace mmu audit tracepoint with jump-label
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>
2011-12-27 11:22:05 +02:00
Sasha Levin 831bf664e9 KVM: Refactor and simplify kvm_dev_ioctl_get_supported_cpuid
This patch cleans and simplifies kvm_dev_ioctl_get_supported_cpuid by using a table
instead of duplicating code as Avi suggested.

This patch also fixes a bug where kvm_dev_ioctl_get_supported_cpuid would return
-E2BIG when amount of entries passed was just right.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:22:02 +02:00
Liu, Jinsong fb215366b3 KVM: expose latest Intel cpu new features (BMI1/BMI2/FMA/AVX2) to guest
Intel latest cpu add 6 new features, refer http://software.intel.com/file/36945
The new feature cpuid listed as below:

1. FMA		CPUID.EAX=01H:ECX.FMA[bit 12]
2. MOVBE	CPUID.EAX=01H:ECX.MOVBE[bit 22]
3. BMI1		CPUID.EAX=07H,ECX=0H:EBX.BMI1[bit 3]
4. AVX2		CPUID.EAX=07H,ECX=0H:EBX.AVX2[bit 5]
5. BMI2		CPUID.EAX=07H,ECX=0H:EBX.BMI2[bit 8]
6. LZCNT	CPUID.EAX=80000001H:ECX.LZCNT[bit 5]

This patch expose these features to guest.
Among them, FMA/MOVBE/LZCNT has already been defined, MOVBE/LZCNT has
already been exposed.

This patch defines BMI1/AVX2/BMI2, and exposes FMA/BMI1/AVX2/BMI2 to guest.

Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:22:01 +02:00
Avi Kivity 00b27a3efb KVM: Move cpuid code to new file
The cpuid code has grown; put it into a separate file.

Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:21:49 +02:00
Takuya Yoshikawa 2b5e97e1fa KVM: x86 emulator: Use opcode::execute for INS/OUTS from/to port in DX
INSB       : 6C
INSW/INSD  : 6D
OUTSB      : 6E
OUTSW/OUTSD: 6F

The I/O port address is read from the DX register when we decode the
operand because we see the SrcDX/DstDX flag is set.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:17:46 +02:00
Xiao Guangrong 28a37544fb KVM: introduce id_to_memslot function
Introduce id_to_memslot to get memslot by slot id

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:17:39 +02:00
Xiao Guangrong be6ba0f096 KVM: introduce kvm_for_each_memslot macro
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>
2011-12-27 11:17:37 +02:00
Xiao Guangrong be593d6286 KVM: introduce update_memslots function
Introduce update_memslots to update slot which will be update to
kvm->memslots

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:17:35 +02:00
Xiao Guangrong 93a5cef07d KVM: introduce KVM_MEM_SLOTS_NUM macro
Introduce KVM_MEM_SLOTS_NUM macro to instead of
KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:17:34 +02:00
Takuya Yoshikawa ff227392cd KVM: x86 emulator: Use opcode::execute for BSF/BSR
BSF: 0F BC
BSR: 0F BD

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:17:32 +02:00
Takuya Yoshikawa e940b5c20f KVM: x86 emulator: Use opcode::execute for CMPXCHG
CMPXCHG: 0F B0, 0F B1

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:17:31 +02:00
Takuya Yoshikawa e1e210b0a7 KVM: x86 emulator: Use opcode::execute for WRMSR/RDMSR
WRMSR: 0F 30
RDMSR: 0F 32

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:17:29 +02:00
Takuya Yoshikawa bc00f8d2c2 KVM: x86 emulator: Use opcode::execute for MOV to cr/dr
MOV: 0F 22 (move to control registers)
MOV: 0F 23 (move to debug registers)

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:17:28 +02:00
Takuya Yoshikawa d4ddafcdf2 KVM: x86 emulator: Use opcode::execute for CALL
CALL: E8

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:17:26 +02:00
Takuya Yoshikawa ce7faab24f KVM: x86 emulator: Use opcode::execute for BT family
BT : 0F A3
BTS: 0F AB
BTR: 0F B3
BTC: 0F BB

Group 8: 0F BA

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:17:25 +02:00
Takuya Yoshikawa d7841a4b1b KVM: x86 emulator: Use opcode::execute for IN/OUT
IN : E4, E5, EC, ED
OUT: E6, E7, EE, EF

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2011-12-27 11:17:23 +02:00
Gleb Natapov 46199f33c2 KVM: VMX: remove unneeded vmx_load_host_state() calls.
vmx_load_host_state() does not handle msrs switching (except
MSR_KERNEL_GS_BASE) since commit 26bb0981b3. Remove call to it
where it is no longer make sense.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:17:22 +02:00
Takuya Yoshikawa 95d4c16ce7 KVM: Optimize dirty logging by rmap_write_protect()
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>
2011-12-27 11:17:20 +02:00
Takuya Yoshikawa 7850ac5420 KVM: Count the number of dirty pages for dirty logging
Needed for the next patch which uses this number to decide how to write
protect a slot.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-27 11:17:19 +02:00