Message-ID: <9461b569-2f76-0ec7-af8d-53ee0778b7cd@intel.com>
Date:   Mon, 13 Mar 2023 08:42:11 -0700
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Subject: Re: [PATCH -v2] x86/CPU/AMD: Make sure EFER[AIBRSE] is set
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To:     Borislav Petkov <bp@alien8.de>
Cc:     Josh Poimboeuf <jpoimboe@kernel.org>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
        Kim Phillips <kim.phillips@amd.com>, x86@kernel.org,
        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>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Alexey Kardashevskiy <aik@amd.com>, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <Y/knUC0s+rg6ef2r@zn.tnic> <Y/k/ZXUXOFiBhOiI@zn.tnic>
 <20230225000931.wrednfun4jifkqau@treble> <Y/lUSC5x2ZkTIGu4@zn.tnic>
 <20230225005221.425yahqvxb57c43x@desk>
 <20230225013202.g7tibykvylprsxs5@treble> <Y/n9XcbnCzWv2Vul@zn.tnic>
 <445daef5-8417-ddbb-abbf-3c5ab38e1c9c@intel.com> <Y/zO7MtvjiVLCiLg@zn.tnic>
 <3f80e71f-a995-8ad6-b7f2-2b80fefdbd46@intel.com>
 <20230310162253.GCZAtZXcpK2JK0cFkZ@fat_crate.local>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <20230310162253.GCZAtZXcpK2JK0cFkZ@fat_crate.local>
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On 3/10/23 08:22, Borislav Petkov wrote:
> The AutoIBRS bit gets set only on the BSP as part of determining which
> mitigation to enable on AMD. Setting on the APs relies on the
> circumstance that the APs get booted through the trampoline and EFER
> - the MSR which contains that bit - gets replicated on every AP from the
> BSP.
> 
> However, this can change in the future and considering the security
> implications of this bit not being set on every CPU, make sure it is set
> by verifying EFER later in the boot process and on every AP.
> 
> Reported-by: Josh Poimboeuf <jpoimboe@kernel.org>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> Link: https://lore.kernel.org/r/20230224185257.o3mcmloei5zqu7wa@treble

Looks sane, thanks for adding the warning:

Acked-by: Dave Hansen <dave.hansen@linux.intel.com>