linux-kernel - Re: [PATCH v8 0/8] x86/cpu, kvm: Support AMD Automatic IBRS

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Date:   Tue, 24 Jan 2023 01:18:57 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Kim Phillips <kim.phillips@....com>
Cc:     x86@...nel.org, Borislav Petkov <bp@...en8.de>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Luck <tony.luck@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Alexey Kardashevskiy <aik@....com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 0/8] x86/cpu, kvm: Support AMD Automatic IBRS

On Mon, Jan 23, 2023, Kim Phillips wrote:
> The AMD Zen4 core supports a new feature called Automatic IBRS
> (Indirect Branch Restricted Speculation).
> 
> Enable Automatic IBRS by default if the CPU feature is present.
> It typically provides greater performance over the incumbent
> generic retpolines mitigation.
> 
> Patch 1 [unchanged from v7] Adds support for the leaf that
> contains the AutoIBRS feature bit.
> 
> Patch 2 moves the leaf's open-coded code from __do_cpuid_func()
> to kvm_set_cpu_caps() in preparation for adding the features in
> their native leaf.
> 
> Patches 3-6 introduce the new leaf's supported bits one by one.
> 
> Patch 7 [unchanged from v7] Adds support for AutoIBRS by turning
> its EFER enablement bit on at startup if the feature is available.
> 
> Patch 8 [unchanged from v7] Adds support for propagating AutoIBRS
> to the guest.

A few nits, but otherwise looks good.  Thanks!