linux-kernel - Re: [PATCH] KVM: SVM: Assume a 64-bit hypercall for guests with protected state

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Date:   Mon, 24 May 2021 11:05:58 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Brijesh Singh <brijesh.singh@....com>,
        Ashish Kalra <Ashish.Kalra@....com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] KVM: SVM: Assume a 64-bit hypercall for guests with
 protected state

On 5/24/21 9:20 AM, Paolo Bonzini wrote:
> On 24/05/21 15:58, Tom Lendacky wrote:
>>> Would it hurt if we just move 'vcpu->arch.guest_state_protected' check
>>> to is_64_bit_mode() itself? It seems to be too easy to miss this
>>> peculiar detail about SEV in review if new is_64_bit_mode() users are to
>>> be added.
>> I thought about that, but wondered if is_64_bit_mode() was to be used in
>> other places in the future, if it would be a concern. I think it would be
>> safe since anyone adding it to a new section of code is likely to look at
>> what that function is doing first.
>>
>> I'm ok with this. Paolo, I know you already queued this, but would you
>> prefer moving the check into is_64_bit_mode()?
> 
> Let's introduce a new wrapper is_64_bit_hypercall, and add a
> WARN_ON_ONCE(vcpu->arch.guest_state_protected) to is_64_bit_mode.

Will do.

Thanks,
Tom

> 
> Paolo
>