Re: [PATCH] KVM: x86: Fix the intel_pt PMI handling wrongly considered from guest

[Yanfei Xu]

On 2022/5/16 21:58, Sean Christopherson wrote:
> On Mon, May 16, 2022, Yanfei Xu wrote:
> > When kernel handles the vm-exit caused by external interrupts and PMI,
> > it always set a type of kvm_intr_type to handling_intr_from_guest to
> > tell if it's dealing an IRQ or NMI.
> > However, the further type judgment is missing in kvm_arch_pmi_in_guest().
> > It could make the PMI of intel_pt wrongly considered it comes from a
> > guest once the 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@xxxxxxxxx>
> > ---
> >   arch/x86/include/asm/kvm_host.h | 8 +++++++-
> >   arch/x86/kvm/x86.h              | 6 ------
> >   2 files changed, 7 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 4ff36610af6a..308cf19f123d 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1582,8 +1582,14 @@ static inline int kvm_arch_flush_remote_tlb(struct kvm *kvm)
> >   		return -ENOTSUPP;
> >   }
> >   
> > +enum kvm_intr_type {
> > +	/* Values are arbitrary, but must be non-zero. */
> > +	KVM_HANDLING_IRQ = 1,
> > +	KVM_HANDLING_NMI,
> > +};
> > +
> >   #define kvm_arch_pmi_in_guest(vcpu) \
> > -	((vcpu) && (vcpu)->arch.handling_intr_from_guest)
> > +	((vcpu) && (vcpu)->arch.handling_intr_from_guest == KVM_HANDLING_NMI)
> My understanding is that this isn't correct as a general change, as perf events
> can use regular IRQs in some cases.  See commit dd60d217062f4 ("KVM: x86: Fix perf
> timer mode IP reporting").
>
> I assume there's got to be a way to know which mode perf is using, e.g. we should
> be able to make this look something like:
>
> 	((vcpu) && (vcpu)->arch.handling_intr_from_guest == kvm_pmi_vector)

Thanks for your comments, I am going to understand these clearly and 
then reply or give a next version.

Regards,
Yanfei

> >   void kvm_mmu_x86_module_init(void);
> >   int kvm_mmu_vendor_module_init(void);
> > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> > index 588792f00334..3bdf1bc76863 100644
> > --- a/arch/x86/kvm/x86.h
> > +++ b/arch/x86/kvm/x86.h
> > @@ -344,12 +344,6 @@ static inline bool kvm_cstate_in_guest(struct kvm *kvm)
> >   	return kvm->arch.cstate_in_guest;
> >   }
> >   
> > -enum kvm_intr_type {
> > -	/* Values are arbitrary, but must be non-zero. */
> > -	KVM_HANDLING_IRQ = 1,
> > -	KVM_HANDLING_NMI,
> > -};
> > -
> >   static inline void kvm_before_interrupt(struct kvm_vcpu *vcpu,
> >   					enum kvm_intr_type intr)
> >   {
> > --
> > 2.32.0