linux-kernel - Re: [PATCH 3/4] KVM: x86: pending exception must be be injected even with an injected event

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Date:   Thu, 25 Feb 2021 17:05:14 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Ingo Molnar <mingo@...hat.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>, Jim Mattson <jmattson@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wanpeng Li <wanpengli@...cent.com>,
        Sean Christopherson <seanjc@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 3/4] KVM: x86: pending exception must be be injected even
 with an injected event

On 25/02/21 16:41, Maxim Levitsky wrote:
> Injected events should not block a pending exception, but rather,
> should either be lost or be delivered to the nested hypervisor as part of
> exitintinfo/IDT_VECTORING_INFO
> (if nested hypervisor intercepts the pending exception)
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>

Does this already fix some of your new test cases?

Paolo

> ---
>   arch/x86/kvm/svm/nested.c | 7 ++++++-
>   arch/x86/kvm/vmx/nested.c | 9 +++++++--
>   2 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index 881e3954d753b..4c82abce0ea0c 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -1024,7 +1024,12 @@ static int svm_check_nested_events(struct kvm_vcpu *vcpu)
>   	}
>   
>   	if (vcpu->arch.exception.pending) {
> -		if (block_nested_events)
> +		/*
> +		 * Only pending nested run can block an pending exception
> +		 * Otherwise an injected NMI/interrupt should either be
> +		 * lost or delivered to the nested hypervisor in EXITINTINFO
> +		 * */
> +		if (svm->nested.nested_run_pending)
>                           return -EBUSY;
>   		if (!nested_exit_on_exception(svm))
>   			return 0;
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index b34e284bfa62a..20ed1a351b2d9 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -3810,9 +3810,14 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
>   
>   	/*
>   	 * Process any exceptions that are not debug traps before MTF.
> +	 *
> +	 * Note that only pending nested run can block an pending exception
> +	 * Otherwise an injected NMI/interrupt should either be
> +	 * lost or delivered to the nested hypervisor in EXITINTINFO
>   	 */
> +
>   	if (vcpu->arch.exception.pending && !vmx_pending_dbg_trap(vcpu)) {
> -		if (block_nested_events)
> +		if (vmx->nested.nested_run_pending)
>   			return -EBUSY;
>   		if (!nested_vmx_check_exception(vcpu, &exit_qual))
>   			goto no_vmexit;
> @@ -3829,7 +3834,7 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
>   	}
>   
>   	if (vcpu->arch.exception.pending) {
> -		if (block_nested_events)
> +		if (vmx->nested.nested_run_pending)
>   			return -EBUSY;
>   		if (!nested_vmx_check_exception(vcpu, &exit_qual))
>   			goto no_vmexit;
>