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Date:   Fri, 4 Nov 2022 15:06:28 -0700
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Subject: Re: [PATCH 0/3] x86/speculation: Support Automatic IBRS
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To:     Kim Phillips <kim.phillips@amd.com>, x86@kernel.org
Cc:     Borislav Petkov <bp@alien8.de>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Joao Martins <joao.m.martins@oracle.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        David Woodhouse <dwmw@amazon.co.uk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Juergen Gross <jgross@suse.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Tony Luck <tony.luck@intel.com>,
        Babu Moger <Babu.Moger@amd.com>,
        Tom Lendacky <thomas.lendacky@amd.com>, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20221104213651.141057-1-kim.phillips@amd.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <20221104213651.141057-1-kim.phillips@amd.com>
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On 11/4/22 14:36, 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.

Could you also share some information on how this differs from EIBRS and
why it needs to exist in parallel to EBIRS?