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

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Message-ID: <e70aa81d-95d6-9a89-2e34-f5e5974b40f1@intel.com>
Date:   Wed, 18 May 2022 18:01:56 +0800
From:   Yanfei Xu <yanfei.xu@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     <pbonzini@...hat.com>, <vkuznets@...hat.com>,
        <wanpengli@...cent.com>, <jmattson@...gle.com>, <joro@...tes.org>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86: Fix the intel_pt PMI handling wrongly
 considered from guest


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@...el.com>
>> ---
>>   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
>>