A Xen HVM guest running with KASLR enabled will die rather soon today
because the shared info page mapping is using va() too early. This was
introduced by commit a5d5f328b0 ("xen:
allocate page for shared info page from low memory").
In order to fix this use early_memremap() to get a temporary virtual
address for shared info until va() can be used safely.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Instead of calling xen_hvm_init_shared_info() on boot and resume split
it up into a boot time function searching for the pfn to use and a
mapping function doing the hypervisor mapping call.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
In a HVM guest the kernel allocates the page for mapping the shared
info structure via extend_brk() today. This will lead to a drop of
performance as the underlying EPT entry will have to be split up into
4kB entries as the single shared info page is located in hypervisor
memory.
The issue has been detected by using the libmicro munmap test:
unmapping 8kB of memory was faster by nearly a factor of two when no
pv interfaces were active in the HVM guest.
So instead of taking a page from memory which might be mapped via
large EPT entries use a page which is already mapped via a 4kB EPT
entry: we can take a page from the first 1MB of memory as the video
memory at 640kB disallows using larger EPT entries.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
The hypercall VCPUOP_register_vcpu_info can fail. This failure is
handled by making per_cpu(xen_vcpu, cpu) point to its shared_info
slot and those without one (cpu >= MAX_VIRT_CPUS) be NULL.
For PVH/PVHVM, this is not enough, because we also need to pull
these VCPUs out of circulation.
Fix for PVH/PVHVM: on registration failure in the cpuhp prepare
callback (xen_cpu_up_prepare_hvm()), return an error to the cpuhp
state-machine so it can fail the CPU init.
Fix for PV: the registration happens before smp_init(), so, in the
failure case we clamp setup_max_cpus and limit the number of VCPUs
that smp_init() will bring-up to MAX_VIRT_CPUS.
This is functionally correct but it makes the code a bit simpler
if we get rid of this explicit clamping: for VCPUs that don't have
valid xen_vcpu, fail the CPU init in the cpuhp prepare callback
(xen_cpu_up_prepare_pv()).
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
When Xen restores a PVHVM or PVH guest, its shared_info only holds
up to 32 CPUs. The hypercall VCPUOP_register_vcpu_info allows
us to setup per-page areas for VCPUs. This means we can boot
PVH* guests with more than 32 VCPUs. During restore the per-cpu
structure is allocated freshly by the hypervisor (vcpu_info_mfn is
set to INVALID_MFN) so that the newly restored guest can make a
VCPUOP_register_vcpu_info hypercall.
However, we end up triggering this condition in Xen:
/* Run this command on yourself or on other offline VCPUS. */
if ( (v != current) && !test_bit(_VPF_down, &v->pause_flags) )
which means we are unable to setup the per-cpu VCPU structures
for running VCPUS. The Linux PV code paths makes this work by
iterating over cpu_possible in xen_vcpu_restore() with:
1) is target CPU up (VCPUOP_is_up hypercall?)
2) if yes, then VCPUOP_down to pause it
3) VCPUOP_register_vcpu_info
4) if it was down, then VCPUOP_up to bring it back up
With Xen commit 192df6f9122d ("xen/x86: allow HVM guests to use
hypercalls to bring up vCPUs") this is available for non-PV guests.
As such first check if VCPUOP_is_up is actually possible before
trying this dance.
As most of this dance code is done already in xen_vcpu_restore()
let's make it callable on PV, PVH and PVHVM.
Based-on-patch-by: Konrad Wilk <konrad.wilk@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Largely mechanical changes to aid unification of xen_vcpu_restore()
logic for PV, PVH and PVHVM.
xen_vcpu_setup(): the only change in logic is that clamp_max_cpus()
is now handled inside the "if (!xen_have_vcpu_info_placement)" block.
xen_vcpu_restore(): code movement from enlighten_pv.c to enlighten.c.
xen_vcpu_info_reset(): pulls together all the code where xen_vcpu
is set to default.
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Commit 84d582d236 ("xen: Revert commits da72ff5bfc and
72a9b186292d") defined xen_have_vector_callback in enlighten_hvm.c.
Since guest-type-neutral code refers to this variable this causes
build failures when CONFIG_XEN_PVHVM is not defined.
Moving xen_have_vector_callback definition to enlighten.c resolves
this issue.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Recent discussion (http://marc.info/?l=xen-devel&m=149192184523741)
established that commit 72a9b18629 ("xen: Remove event channel
notification through Xen PCI platform device") (and thus commit
da72ff5bfc ("partially revert "xen: Remove event channel
notification through Xen PCI platform device"")) are unnecessary and,
in fact, prevent HVM guests from booting on Xen releases prior to 4.0
Therefore we revert both of those commits.
The summary of that discussion is below:
Here is the brief summary of the current situation:
Before the offending commit (72a9b18629):
1) INTx does not work because of the reset_watches path.
2) The reset_watches path is only taken if you have Xen > 4.0
3) The Linux Kernel by default will use vector inject if the hypervisor
support. So even INTx does not work no body running the kernel with
Xen > 4.0 would notice. Unless he explicitly disabled this feature
either in the kernel or in Xen (and this can only be disabled by
modifying the code, not user-supported way to do it).
After the offending commit (+ partial revert):
1) INTx is no longer support for HVM (only for PV guests).
2) Any HVM guest The kernel will not boot on Xen < 4.0 which does
not have vector injection support. Since the only other mode
supported is INTx which.
So based on this summary, I think before commit (72a9b18629) we were
in much better position from a user point of view.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Move PVHVM related code to enlighten_hvm.c. Three functions:
xen_cpuhp_setup(), xen_reboot(), xen_emergency_restart() are shared, drop
static qualifier from them. These functions will go to common code once
it is split from enlighten.c.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Juergen Gross