linux-kernel - Re: [PATCH v2] KVM: SVM: Fix potential wrong physical id in avic_handle_ldr

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Date:   Tue, 22 Oct 2019 18:47:58 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, rkrcmar@...hat.com,
        sean.j.christopherson@...el.com, vkuznets@...hat.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com
Cc:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingfangsen@...wei.com
Subject: Re: [PATCH v2] KVM: SVM: Fix potential wrong physical id in
 avic_handle_ldr_update

On 18/10/19 04:50, Miaohe Lin wrote:
> Guest physical APIC ID may not equal to vcpu->vcpu_id in some case.
> We may set the wrong physical id in avic_handle_ldr_update as we
> always use vcpu->vcpu_id. Get physical APIC ID from vAPIC page
> instead.
> Export and use kvm_xapic_id here and in avic_handle_apic_id_update
> as suggested by Vitaly.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  arch/x86/kvm/lapic.c | 5 -----
>  arch/x86/kvm/lapic.h | 5 +++++
>  arch/x86/kvm/svm.c   | 6 +++---
>  3 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 87b0fcc23ef8..b29d00b661ff 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -111,11 +111,6 @@ static inline int apic_enabled(struct kvm_lapic *apic)
>  	(LVT_MASK | APIC_MODE_MASK | APIC_INPUT_POLARITY | \
>  	 APIC_LVT_REMOTE_IRR | APIC_LVT_LEVEL_TRIGGER)
>  
> -static inline u8 kvm_xapic_id(struct kvm_lapic *apic)
> -{
> -	return kvm_lapic_get_reg(apic, APIC_ID) >> 24;
> -}
> -
>  static inline u32 kvm_x2apic_id(struct kvm_lapic *apic)
>  {
>  	return apic->vcpu->vcpu_id;
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index 2aad7e226fc0..1f5014852e20 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -242,4 +242,9 @@ static inline enum lapic_mode kvm_apic_mode(u64 apic_base)
>  	return apic_base & (MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE);
>  }
>  
> +static inline u8 kvm_xapic_id(struct kvm_lapic *apic)
> +{
> +	return kvm_lapic_get_reg(apic, APIC_ID) >> 24;
> +}
> +
>  #endif
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index f8ecb6df5106..ca200b50cde4 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -4591,6 +4591,7 @@ static int avic_handle_ldr_update(struct kvm_vcpu *vcpu)
>  	int ret = 0;
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  	u32 ldr = kvm_lapic_get_reg(vcpu->arch.apic, APIC_LDR);
> +	u32 id = kvm_xapic_id(vcpu->arch.apic);
>  
>  	if (ldr == svm->ldr_reg)
>  		return 0;
> @@ -4598,7 +4599,7 @@ static int avic_handle_ldr_update(struct kvm_vcpu *vcpu)
>  	avic_invalidate_logical_id_entry(vcpu);
>  
>  	if (ldr)
> -		ret = avic_ldr_write(vcpu, vcpu->vcpu_id, ldr);
> +		ret = avic_ldr_write(vcpu, id, ldr);
>  
>  	if (!ret)
>  		svm->ldr_reg = ldr;
> @@ -4610,8 +4611,7 @@ static int avic_handle_apic_id_update(struct kvm_vcpu *vcpu)
>  {
>  	u64 *old, *new;
>  	struct vcpu_svm *svm = to_svm(vcpu);
> -	u32 apic_id_reg = kvm_lapic_get_reg(vcpu->arch.apic, APIC_ID);
> -	u32 id = (apic_id_reg >> 24) & 0xff;
> +	u32 id = kvm_xapic_id(vcpu->arch.apic);
>  
>  	if (vcpu->vcpu_id == id)
>  		return 0;
> 

Queued, thanks.

Paolo