linux-kernel - Re: [PATCH 2/3] KVM: SVM: Move svm_complete_interrupts() into svm_vcpu

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Date:   Wed, 09 Sep 2020 10:35:55 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        "Paul K ." <kronenpj@...nenpj.dyndns.org>
Subject: Re: [PATCH 2/3] KVM: SVM: Move svm_complete_interrupts() into svm_vcpu_run()

Wanpeng Li <kernellwp@...il.com> writes:

> From: Wanpeng Li <wanpengli@...cent.com>
>
> Moving svm_complete_interrupts() into svm_vcpu_run() which can align VMX 
> and SVM with respect to completing interrupts.
>
> Suggested-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Cc: Paul K. <kronenpj@...nenpj.dyndns.org>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> ---
>  arch/x86/kvm/svm/svm.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index c61bc3b..74bcf0a 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -2938,8 +2938,6 @@ static int handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
>  	if (npt_enabled)
>  		vcpu->arch.cr3 = svm->vmcb->save.cr3;
>  
> -	svm_complete_interrupts(svm);
> -
>  	if (is_guest_mode(vcpu)) {
>  		int vmexit;
>  
> @@ -3530,6 +3528,8 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
>  		     SVM_EXIT_EXCP_BASE + MC_VECTOR))
>  		svm_handle_mce(svm);
>  
> +	svm_complete_interrupts(svm);
> +
>  	vmcb_mark_all_clean(svm->vmcb);
>  	return exit_fastpath;
>  }

This seems to be the right thing to do, however, the amount of code
between kvm_x86_ops.run() and kvm_x86_ops.handle_exit() is non-trivial,
hope it won't blow up in testing...

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

One more thing:

VMX version does

        vmx_complete_interrupts(vmx);
        if (is_guest_mode(vcpu))
                return EXIT_FASTPATH_NONE;

and on SVM we analyze is_guest_mode() inside
svm_exit_handlers_fastpath() - should we also change that for
conformity?

-- 
Vitaly