Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210430131733.192414-1-rsaripal@amd.com> <20210430131733.192414-2-rsaripal@amd.com>
 <CAAeT=Fw-nt5h3DhRCQr8Ma71NiP7dHB+WD2hie_55SpCHR=mDQ@mail.gmail.com> <e53887f8-c09d-28db-5041-bf8822370c46@amd.com>
In-Reply-To: <e53887f8-c09d-28db-5041-bf8822370c46@amd.com>
From:   Reiji Watanabe <reijiw@google.com>
Date:   Fri, 30 Apr 2021 18:50:26 -0700
Message-ID: <CAAeT=FyAmSxKy5cpGLBH_kqDohXeQOdi4r02KjQO_vycq=4y=Q@mail.gmail.com>
Subject: Re: [PATCH v4 1/1] x86/cpufeatures: Implement Predictive Store
 Forwarding control.
To:     "Saripalli, RK" <rsaripal@amd.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de,
        mingo@redhat.com, Borislav Petkov <bp@alien8.de>, hpa@zytor.com,
        Jonathan Corbet <corbet@lwn.net>, bsd@redhat.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

> > Considering KVM/virtualization for a CPU that has X86_FEATURE_PSFD
> > but no other existing feature with MSR_IA32_SPEC_CTRL, if a host
> > doesn't enable PSFD with the new parameter, the host doesn't have
> > X86_FEATURE_MSR_SPEC_CTRL.  Then, it would be a problem if its
> > guests want to use PSFD looking at x86_virt_spec_ctrl().
> > (I'm not sure how you will change your previous KVM patch though)
>
> Reiji, you are correct that X86_FEATURE_MSR_SPEC_CTRL should be enabled so KVM guests can use PSFD
> even if host does not use it.
> I have this change in my KVM patch.


Thank you for the response. Yes, that sounds good.

Thanks,
Reiji