Subject: Re: [PATCH 0/7] KVM: x86: expose CVE-2017-5715 ("Spectre variant 2")
 mitigations to guest
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        jmattson@google.com, aliguori@amazon.com, thomas.lendacky@amd.com,
        dwmw@amazon.co.uk, bp@alien8.de
References: <1515434925-10250-1-git-send-email-pbonzini@redhat.com>
 <alpine.DEB.2.20.1801091113210.1766@nanos>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <d608fd65-ccbe-d87b-33b1-20b3a0c8cea7@redhat.com>
Date: Tue, 9 Jan 2018 12:12:00 +0100
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Sender: linux-kernel-owner@vger.kernel.org

On 09/01/2018 11:15, Thomas Gleixner wrote:
> On Mon, 8 Jan 2018, Paolo Bonzini wrote:
> 
>> This series allows guests to use the MSR_IA32_SPEC_CTRL and
>> MSR_IA32_PRED_CMD model specific registers that were added as mitigations
>> for CVE-2017-5715.
>>
>> These are only the KVM specific parts of the fix.  It does *not* yet
>> include any protection for reading host memory from the guest, because
>> that would be done in the same way as the rest of Linux.  So there is no
>> IBRS *usage* here, no retpolines, no stuffing of the return stack buffer.
>> (KVM already includes a fix to clear all registers on vmexit, which is
>> enough to block Google Project Zero's PoC exploit).
>>
>> However, I am including the changes to use IBPB (indirect branch
>> predictor barrier) if available.  That occurs only when there is a VCPU
>> switch on a physical CPU, thus it has a small impact on performance.
>>
>> The patches are a bit hackish because the relevant cpufeatures have
>> not been included yet, and because I wanted to make the patches easier
>> to backport to distro kernels if desired, but I would still like to
>> have them in 4.16.
>>
>> Please review.
> 
> CC'ing x86@kernel.org on this would have been asked too much, right?

Sorry, my mistake.  I'll CC you on v2.

Paolo