linux-kernel - Re: [PATCH v5 2/2] kvm: nVMX: Introduce KVM_CAP_NESTED

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Message-ID: <8653119f-0ac4-7937-225b-16ef0977528b@redhat.com>
Date:   Wed, 18 Jul 2018 23:10:10 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jim Mattson <jmattson@...gle.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     KarimAllah Ahmed <karahmed@...zon.de>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH v5 2/2] kvm: nVMX: Introduce KVM_CAP_NESTED_STATE

On 18/07/2018 20:03, Jim Mattson wrote:
> On Wed, Jul 18, 2018 at 10:55 AM, Radim Krčmář <rkrcmar@...hat.com> wrote:
> 
>>> +     vmx->nested.nested_run_pending = 1;
>> This is not necessary.  We're only copying state and do not add anything
>> that would be lost on a nested VM exit without prior VM entry.
> If nested_run_pending is blindly set on restore, then prepare_vmcs02
> will do the wrong thing. For example, if there was an injected event
> in the vmcs12, it will get injected again, even if the vCPU has been
> in L2 for some time.
> 
> The value of nested_run_pending should always come from the saved VMX
> state (a few lines above).
> 

Yep, and there are a couple other things that need adjustment.  Stay
tuned...

Paolo