linux-kernel - Re: [PATCH] KVM: x86: Expose Predictive Store Forwarding Disable

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Message-ID: <b28c0e56-59b3-1152-56ef-490887cb0d87@redhat.com>
Date:   Fri, 26 Aug 2022 12:10:44 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     Babu Moger <babu.moger@....com>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        seanjc@...gle.com, vkuznets@...hat.com, wanpengli@...cent.com,
        joro@...tes.org, tony.luck@...el.com, peterz@...radead.org,
        kyung.min.park@...el.com, wei.huang2@....com, jgross@...e.com,
        andrew.cooper3@...rix.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Expose Predictive Store Forwarding Disable

On 8/24/22 19:16, Jim Mattson wrote:
>> Borislav asked to not show psfd in /proc/cpuinfo, because Linux had
>> decided not to control PSF separately; instead it just piggybacked
>> on SSBD which should disable PSF as well.  Honestly I disagree but
>> it's not my area of maintenance.
> 
> Do we expose PSFD in KVM for the use of another popular guest OS?

Yes, that was the purpose of this patch and we expose it via 
MSR_IA32_SPEC_CTRL (the only validation that KVM does is in 
kvm_spec_ctrl_test_value(), so it does not need to know more about the 
specific bits).

Paolo