arch/x86/kvm/vmx/vmx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
When kernel handles the vm-exit caused by external interrupts and NMI,
it always set a type of kvm_intr_type to handling_intr_from_guest to
tell if it's dealing an IRQ or NMI. For the PMI scenario, it could be
IRQ or NMI.
However the intel_pt PMI certainly is a NMI PMI, hence using
kvm_handling_nmi_from_guest() to distinguish if the intel_pt PMI comes
from guest is more appropriate. This modification can avoid the host
wrongly considered the intel_pt PMI comes from a guest once the host
intel_pt PMI breaks the handling of vm-exit of external interrupts.
Fixes: db215756ae59 ("KVM: x86: More precisely identify NMI from guest when handling PMI")
Signed-off-by: Yanfei Xu <yanfei.xu@intel.com>
---
v1->v2:
1.Fix vmx_handle_intel_pt_intr() directly instead of changing the generic function.
2.Tune the commit message.
v2->v3:
Add the NULL pointer check of variable "vcpu".
arch/x86/kvm/vmx/vmx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 610355b9ccce..982df9c000d3 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7856,7 +7856,7 @@ static unsigned int vmx_handle_intel_pt_intr(void)
struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
/* '0' on failure so that the !PT case can use a RET0 static call. */
- if (!kvm_arch_pmi_in_guest(vcpu))
+ if (!vcpu || !kvm_handling_nmi_from_guest(vcpu))
return 0;
kvm_make_request(KVM_REQ_PMI, vcpu);
--
2.32.0
Queued, thanks. Paolo
On Mon, May 23, 2022, Yanfei Xu wrote: > When kernel handles the vm-exit caused by external interrupts and NMI, > it always set a type of kvm_intr_type to handling_intr_from_guest to > tell if it's dealing an IRQ or NMI. For the PMI scenario, it could be > IRQ or NMI. > However the intel_pt PMI certainly is a NMI PMI, hence using It'd be helpful for future readers to explain why it's guaranteed to an NMI. E.g. However, intel_pt PMIs are only generated for HARDWARE perf events, and HARDWARE events are always configured to generate NMIs. Use kvm_handling_nmi_from_guest() to precisely identify if the intel_pt PMI came from the guest to avoid false positives if an intel_pt PMI/NMI arrives while the host is handling an unrelated IRQ VM-Exit. > kvm_handling_nmi_from_guest() to distinguish if the intel_pt PMI comes > from guest is more appropriate. This modification can avoid the host > wrongly considered the intel_pt PMI comes from a guest once the host > intel_pt PMI breaks the handling of vm-exit of external interrupts. > > Fixes: db215756ae59 ("KVM: x86: More precisely identify NMI from guest when handling PMI") > Signed-off-by: Yanfei Xu <yanfei.xu@intel.com> > --- > v1->v2: > 1.Fix vmx_handle_intel_pt_intr() directly instead of changing the generic function. > 2.Tune the commit message. > > v2->v3: > Add the NULL pointer check of variable "vcpu". > > arch/x86/kvm/vmx/vmx.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 610355b9ccce..982df9c000d3 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -7856,7 +7856,7 @@ static unsigned int vmx_handle_intel_pt_intr(void) > struct kvm_vcpu *vcpu = kvm_get_running_vcpu(); > > /* '0' on failure so that the !PT case can use a RET0 static call. */ > - if (!kvm_arch_pmi_in_guest(vcpu)) > + if (!vcpu || !kvm_handling_nmi_from_guest(vcpu)) Alternatively, if (!kvm_arch_pmi_in_guest(vcpu) || !kvm_handling_nmi_from_guest(vcpu)) The generated code is the same since the compiler is smart enough to elide the handling_intr_from_guest check from kvm_arch_pmi_in_guest. I'm not actually sure that's better than the !vcpu check though, e.g. it hides the not-NULL aspect of the check. Either way, with a tweaked changelog, Reviewed-by: Sean Christopherson <seanjc@google.com>
On 2022/5/24 00:43, Sean Christopherson wrote: > On Mon, May 23, 2022, Yanfei Xu wrote: >> When kernel handles the vm-exit caused by external interrupts and NMI, >> it always set a type of kvm_intr_type to handling_intr_from_guest to >> tell if it's dealing an IRQ or NMI. For the PMI scenario, it could be >> IRQ or NMI. >> However the intel_pt PMI certainly is a NMI PMI, hence using > It'd be helpful for future readers to explain why it's guaranteed to an NMI. E.g. > > However, intel_pt PMIs are only generated for HARDWARE perf events, and > HARDWARE events are always configured to generate NMIs. Use > kvm_handling_nmi_from_guest() to precisely identify if the intel_pt PMI > came from the guest to avoid false positives if an intel_pt PMI/NMI > arrives while the host is handling an unrelated IRQ VM-Exit. It's much better! >> kvm_handling_nmi_from_guest() to distinguish if the intel_pt PMI comes >> from guest is more appropriate. This modification can avoid the host >> wrongly considered the intel_pt PMI comes from a guest once the host >> intel_pt PMI breaks the handling of vm-exit of external interrupts. >> >> Fixes: db215756ae59 ("KVM: x86: More precisely identify NMI from guest when handling PMI") >> Signed-off-by: Yanfei Xu <yanfei.xu@intel.com> >> --- >> v1->v2: >> 1.Fix vmx_handle_intel_pt_intr() directly instead of changing the generic function. >> 2.Tune the commit message. >> >> v2->v3: >> Add the NULL pointer check of variable "vcpu". >> >> arch/x86/kvm/vmx/vmx.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >> index 610355b9ccce..982df9c000d3 100644 >> --- a/arch/x86/kvm/vmx/vmx.c >> +++ b/arch/x86/kvm/vmx/vmx.c >> @@ -7856,7 +7856,7 @@ static unsigned int vmx_handle_intel_pt_intr(void) >> struct kvm_vcpu *vcpu = kvm_get_running_vcpu(); >> >> /* '0' on failure so that the !PT case can use a RET0 static call. */ >> - if (!kvm_arch_pmi_in_guest(vcpu)) >> + if (!vcpu || !kvm_handling_nmi_from_guest(vcpu)) > Alternatively, > > if (!kvm_arch_pmi_in_guest(vcpu) || !kvm_handling_nmi_from_guest(vcpu)) > > The generated code is the same since the compiler is smart enough to elide the > handling_intr_from_guest check from kvm_arch_pmi_in_guest. > > I'm not actually sure that's better than the !vcpu check though, e.g. it hides the > not-NULL aspect of the check. > > Either way, with a tweaked changelog, > > Reviewed-by: Sean Christopherson <seanjc@google.com> Thanks Sean. Regards, Yanfei
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