linux-kernel - Re: [PATCH v2 2/2] KVM: nSVM: improve SYSENTER emulation on AMD

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Message-ID: <87zgyic984.fsf@vitty.brq.redhat.com>
Date:   Thu, 01 Apr 2021 17:31:23 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>, "H. Peter Anvin" <hpa@...or.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v2 2/2] KVM: nSVM: improve SYSENTER emulation on AMD

Paolo Bonzini <pbonzini@...hat.com> writes:

> On 01/04/21 15:03, Vitaly Kuznetsov wrote:
>>> +		svm->sysenter_eip_hi = guest_cpuid_is_intel(vcpu) ? (data >> 32) : 0;
>> 
>> (Personal taste) I'd suggest we keep the whole 'sysenter_eip'/'sysenter_esp'
>> even if we only use the upper 32 bits of it. That would reduce the code
>> churn a little bit (no need to change 'struct vcpu_svm').
>
> Would there really be less changes?  Consider that you'd have to look at 
> the VMCB anyway because svm_get_msr can be reached not just for guest 
> RDMSR but also for ioctls.
>

I was thinking about the hunk in arch/x86/kvm/svm/svm.h tweaking
vcpu_svm. My opinion is not strong at all here)

-- 
Vitaly