linux-kernel - Re: [PATCH v2 7/9] KVM: nVMX: Make an event request when pending an MTF nested VM-Exit

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Date:   Wed, 17 Aug 2022 17:11:01 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     seanjc@...gle.com, vkuznets@...hat.com, stable@...r.kernel.org
Subject: Re: [PATCH v2 7/9] KVM: nVMX: Make an event request when pending an
 MTF nested VM-Exit

On Thu, 2022-08-11 at 17:06 -0400, Paolo Bonzini wrote:
> From: Sean Christopherson <seanjc@...gle.com>
> 
> Set KVM_REQ_EVENT when MTF becomes pending to ensure that KVM will run
> through inject_pending_event() and thus vmx_check_nested_events() prior
> to re-entering the guest.
> 
> MTF currently works by virtue of KVM's hack that calls
> kvm_check_nested_events() from kvm_vcpu_running(), but that hack will
> be removed in the near future.  Until that call is removed, the patch
> introduces no functional change.
> 
> Fixes: 5ef8acbdd687 ("KVM: nVMX: Emulate MTF when performing instruction emulation")
> Cc: stable@...r.kernel.org
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d7f8331d6f7e..940c0c0f8281 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1660,10 +1660,12 @@ static void vmx_update_emulated_instruction(struct kvm_vcpu *vcpu)
>          */
>         if (nested_cpu_has_mtf(vmcs12) &&
>             (!vcpu->arch.exception.pending ||
> -            vcpu->arch.exception.nr == DB_VECTOR))
> +            vcpu->arch.exception.nr == DB_VECTOR)) {
>                 vmx->nested.mtf_pending = true;
> -       else
> +               kvm_make_request(KVM_REQ_EVENT, vcpu);
> +       } else {
>                 vmx->nested.mtf_pending = false;
> +       }
>  }
>  
>  static int vmx_skip_emulated_instruction(struct kvm_vcpu *vcpu)

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky