linux-kernel - Re: [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by VM instructions

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Date:   Wed, 13 Jan 2021 13:40:20 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Wei Huang <wei.huang2@....com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        vkuznets@...hat.com, joro@...tes.org, bp@...en8.de,
        tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
        jmattson@...gle.com, wanpengli@...cent.com, bsd@...hat.com,
        dgilbert@...hat.com, mlevitsk@...hat.com
Subject: Re: [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by
 VM instructions

On 12/01/21 18:59, Sean Christopherson wrote:
>> It would be very helpful to list exactly which CPUs are/aren't affected, even if
>> that just means stating something like "all CPUs before XYZ".  Given patch 2/2,
>> I assume it's all CPUs without the new CPUID flag?
> Ah, despite calling this an 'errata', the bad behavior is explicitly documented
> in the APM, i.e. it's an architecture bug, not a silicon bug.

I would still call it an errata for the case when virtualized 
VMSAVE/VMLOAD is enabled (and therefore VMLOAD intercepts are disabled). 
  In that case, the problem is that the GPA does not go through NPT 
before it is checked against *host* reserved memory regions.

In fact I hope that,  on processors that have the fix, VMSAVE/VMLOAD 
from guest mode _does_ check the GPA after it's been translated!

Paolo