* [PATCH] Revert "KVM: nested VMX: disable perf cpuid reporting"
@ 2016-12-21 0:34 Jim Mattson
2016-12-21 9:01 ` David Hildenbrand
2017-01-20 21:21 ` Radim Krčmář
0 siblings, 2 replies; 5+ messages in thread
From: Jim Mattson @ 2016-12-21 0:34 UTC (permalink / raw)
To: kvm; +Cc: Jim Mattson
This reverts commit bc6134942dbbf31c25e9bd7c876be5da81c9e1ce.
A CPUID instruction executed in VMX non-root mode always causes a
VM-exit, regardless of the leaf being queried.
Fixes: bc6134942dbb ("KVM: nested VMX: disable perf cpuid reporting")
Signed-off-by: Jim Mattson <jmattson@google.com>
---
arch/x86/kvm/cpuid.c | 6 ------
arch/x86/kvm/vmx.c | 2 --
2 files changed, 8 deletions(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 84b62ee..4b6e9ab 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -850,12 +850,6 @@ void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
if (!best)
best = check_cpuid_limit(vcpu, function, index);
- /*
- * Perfmon not yet supported for L2 guest.
- */
- if (is_guest_mode(vcpu) && function == 0xa)
- best = NULL;
-
if (best) {
*eax = best->eax;
*ebx = best->ebx;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 64774f4..c7a87ff 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8045,8 +8045,6 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
case EXIT_REASON_TASK_SWITCH:
return true;
case EXIT_REASON_CPUID:
- if (kvm_register_read(vcpu, VCPU_REGS_RAX) == 0xa)
- return false;
return true;
case EXIT_REASON_HLT:
return nested_cpu_has(vmcs12, CPU_BASED_HLT_EXITING);
--
2.8.0.rc3.226.g39d4020
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] Revert "KVM: nested VMX: disable perf cpuid reporting"
2016-12-21 0:34 [PATCH] Revert "KVM: nested VMX: disable perf cpuid reporting" Jim Mattson
@ 2016-12-21 9:01 ` David Hildenbrand
2016-12-21 16:00 ` Jim Mattson
2017-01-20 21:21 ` Radim Krčmář
1 sibling, 1 reply; 5+ messages in thread
From: David Hildenbrand @ 2016-12-21 9:01 UTC (permalink / raw)
To: Jim Mattson, kvm
Am 21.12.2016 um 01:34 schrieb Jim Mattson:
> This reverts commit bc6134942dbbf31c25e9bd7c876be5da81c9e1ce.
>
> A CPUID instruction executed in VMX non-root mode always causes a
> VM-exit, regardless of the leaf being queried.
Makes sense, but wonder if the original problem has been resolved?
--
David
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Revert "KVM: nested VMX: disable perf cpuid reporting"
2016-12-21 9:01 ` David Hildenbrand
@ 2016-12-21 16:00 ` Jim Mattson
2016-12-21 17:48 ` Paolo Bonzini
0 siblings, 1 reply; 5+ messages in thread
From: Jim Mattson @ 2016-12-21 16:00 UTC (permalink / raw)
To: David Hildenbrand; +Cc: kvm
Originally, the L1 hypervisor triggered the following message from L0:
nested_vmx_run: VMCS MSR_{LOAD,STORE} unsupported
This message was removed with commit ff651cb613b4 ("KVM: nVMX: Add
nested msr load/restore algorithm").
It seems likely that this was induced by an attempt to save/restore
MSR_CORE_PERF_GLOBAL_CTRL, since L0 doesn't set the
VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL/VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL
bits in L1's VMX capability MSRs. (As an aside: why not?) This MSR is
virtualized in intel_pmu.c, so I would expect the original problem to
be resolved.
On Wed, Dec 21, 2016 at 1:01 AM, David Hildenbrand <david@redhat.com> wrote:
> Am 21.12.2016 um 01:34 schrieb Jim Mattson:
>>
>> This reverts commit bc6134942dbbf31c25e9bd7c876be5da81c9e1ce.
>>
>> A CPUID instruction executed in VMX non-root mode always causes a
>> VM-exit, regardless of the leaf being queried.
>
>
> Makes sense, but wonder if the original problem has been resolved?
>
> --
>
> David
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Revert "KVM: nested VMX: disable perf cpuid reporting"
2016-12-21 16:00 ` Jim Mattson
@ 2016-12-21 17:48 ` Paolo Bonzini
0 siblings, 0 replies; 5+ messages in thread
From: Paolo Bonzini @ 2016-12-21 17:48 UTC (permalink / raw)
To: Jim Mattson, David Hildenbrand; +Cc: kvm
On 21/12/2016 17:00, Jim Mattson wrote:
>
> It seems likely that this was induced by an attempt to save/restore
> MSR_CORE_PERF_GLOBAL_CTRL, since L0 doesn't set the
> VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL/VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL
> bits in L1's VMX capability MSRs. (As an aside: why not?)
Because no one has ever tried, I guess.
Paolo
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Revert "KVM: nested VMX: disable perf cpuid reporting"
2016-12-21 0:34 [PATCH] Revert "KVM: nested VMX: disable perf cpuid reporting" Jim Mattson
2016-12-21 9:01 ` David Hildenbrand
@ 2017-01-20 21:21 ` Radim Krčmář
1 sibling, 0 replies; 5+ messages in thread
From: Radim Krčmář @ 2017-01-20 21:21 UTC (permalink / raw)
To: Jim Mattson; +Cc: kvm
2016-12-20 16:34-0800, Jim Mattson:
> This reverts commit bc6134942dbbf31c25e9bd7c876be5da81c9e1ce.
>
> A CPUID instruction executed in VMX non-root mode always causes a
> VM-exit, regardless of the leaf being queried.
>
> Fixes: bc6134942dbb ("KVM: nested VMX: disable perf cpuid reporting")
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---
Applied to kvm/queue, thanks.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2016-12-21 0:34 [PATCH] Revert "KVM: nested VMX: disable perf cpuid reporting" Jim Mattson
2016-12-21 9:01 ` David Hildenbrand
2016-12-21 16:00 ` Jim Mattson
2016-12-21 17:48 ` Paolo Bonzini
2017-01-20 21:21 ` Radim Krčmář
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