linux-kernel - Re: [PATCH] KVM: SVM: Add a dedicated INVD intercept routine

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Message-ID: <185c1a30-0028-03c5-6c74-6a4c7ef7f257@amd.com>
Date:   Thu, 24 Sep 2020 08:33:14 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     kvm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Brijesh Singh <brijesh.singh@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] KVM: SVM: Add a dedicated INVD intercept routine

On 9/24/20 1:51 AM, Paolo Bonzini wrote:
> On 23/09/20 22:40, Tom Lendacky wrote:
>>>> +static int invd_interception(struct vcpu_svm *svm)
>>>> +{
>>>> +	/*
>>>> +	 * Can't do emulation on an SEV guest and INVD is emulated
>>>> +	 * as a NOP, so just skip the instruction.
>>>> +	 */
>>>> +	return (sev_guest(svm->vcpu.kvm))
>>>> +		? kvm_skip_emulated_instruction(&svm->vcpu)
>>>> +		: kvm_emulate_instruction(&svm->vcpu, 0);
>>>
>>> Is there any reason not to do kvm_skip_emulated_instruction() for both SEV
>>> and legacy?  VMX has the same odd kvm_emulate_instruction() call, but AFAICT
>>> that's completely unecessary, i.e. VMX can also convert to a straight skip.
>>
>> You could, I just figured I'd leave the legacy behavior just in case. Not
>> that I can think of a reason that behavior would ever change.
> 
> Yeah, let's do skip for both SVM and VMX.

Ok, I'll submit a two patch series to change SVM and VMX. I'll do two 
patches because of the fixes tag to get the SVM fix back to stable. But, 
if you would prefer a single patch, let me know.

Thanks,
Tom

> 
> Paolo
>