linux-kernel - Re: [PATCH 4/6] KVM: nSVM: correctly restore nested_run

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Message-ID: <d4dd81b7bfd4c977ff4b4e1fa6da98e0f06c5fc0.camel@redhat.com>
Date:   Thu, 07 Jan 2021 01:54:00 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     kvm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>, Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 4/6] KVM: nSVM: correctly restore nested_run_pending on
 migration

On Wed, 2021-01-06 at 09:27 -0800, Sean Christopherson wrote:
> On Wed, Jan 06, 2021, Maxim Levitsky wrote:
> > The code to store it on the migration exists, but no code was restoring it.
> > 
> > Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> > ---
> >  arch/x86/kvm/svm/nested.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> > index 6208d3a5a3fdb..c1a3d0e996add 100644
> > --- a/arch/x86/kvm/svm/nested.c
> > +++ b/arch/x86/kvm/svm/nested.c
> > @@ -1203,6 +1203,10 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
> >  	 * in the registers, the save area of the nested state instead
> >  	 * contains saved L1 state.
> >  	 */
> > +
> > +	if (kvm_state->flags & KVM_STATE_NESTED_RUN_PENDING)
> > +		svm->nested.nested_run_pending = true;
> 
> This should be:

Yes, if someone already set the nested state before, but
I also sent a patch that forces nesteded mode exit in this
case.

Still 100% agree, that this would be better.
Thanks for the review,

Best regards,
	Maxim Levitsky

> 
> 	svm->nested.nested_run_pending =
> 		!!(kvm_state->flags & KVM_STATE_NESTED_RUN_PENDING);
> 
> > +
> >  	copy_vmcb_control_area(&hsave->control, &svm->vmcb->control);
> >  	hsave->save = *save;
> >  
> > -- 
> > 2.26.2
> >