linux-kernel - Re: [PATCH v2 16/21] KVM: x86: Evaluate ability to inject SMI/NMI/IRQ after potential VM-Exit

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Date:   Wed, 06 Jul 2022 15:05:17 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Oliver Upton <oupton@...gle.com>,
        Peter Shier <pshier@...gle.com>
Subject: Re: [PATCH v2 16/21] KVM: x86: Evaluate ability to inject
 SMI/NMI/IRQ after potential VM-Exit

On Tue, 2022-06-14 at 20:47 +0000, Sean Christopherson wrote:
> Determine whether or not new events can be injected after checking nested
> events.  If a VM-Exit occurred during nested event handling, any previous
> event that needed re-injection is gone from's KVM perspective; the event
> is captured in the vmc*12 VM-Exit information, but doesn't exist in terms
> of what needs to be done for entry to L1.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/x86.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 930de833aa2b..1a301a1730a5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9502,7 +9502,7 @@ static void kvm_inject_exception(struct kvm_vcpu *vcpu)
>  
>  static int inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
>  {
> -	bool can_inject = !kvm_event_needs_reinjection(vcpu);
> +	bool can_inject;
>  	int r;
>  
>  	/*
> @@ -9567,7 +9567,13 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
>  	if (r < 0)
>  		goto out;
>  
> -	/* try to inject new event if pending */
> +	/*
> +	 * New events, other than exceptions, cannot be injected if KVM needs
> +	 * to re-inject a previous event.  See above comments on re-injecting
> +	 * for why pending exceptions get priority.
> +	 */
> +	can_inject = !kvm_event_needs_reinjection(vcpu);
> +
>  	if (vcpu->arch.exception.pending) {
>  		/*
>  		 * Fault-class exceptions, except #DBs, set RF=1 in the RFLAGS

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

Best regards,
	Maxim Levitsky