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Date:   Mon, 3 Oct 2022 21:54:26 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Dave Hansen <dave.hansen@intel.com>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>
Cc:     Rick Edgecombe <rick.p.edgecombe@intel.com>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@kernel.org>,
        Balbir Singh <bsingharora@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Eugene Syromiatnikov <esyr@redhat.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H . J . Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V . Shankar" <ravi.v.shankar@intel.com>,
        Weijiang Yang <weijiang.yang@intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        joao.moreira@intel.com, John Allen <john.allen@amd.com>,
        kcc@google.com, eranian@google.com, rppt@kernel.org,
        jamorris@linux.microsoft.com, dethoma@microsoft.com,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "Moger, Babu" <babu.moger@amd.com>
Subject: Re: [PATCH v2 33/39] x86/cpufeatures: Limit shadow stack to Intel
 CPUs
Message-ID: <202210032147.ED1310CEA8@keescook>
References: <20220929222936.14584-1-rick.p.edgecombe@intel.com>
 <20220929222936.14584-34-rick.p.edgecombe@intel.com>
 <202210031656.23FAA3195@keescook>
 <559f937f-cab4-d408-6d95-fc85b4809aa9@intel.com>
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On Mon, Oct 03, 2022 at 05:09:04PM -0700, Dave Hansen wrote:
> On 10/3/22 16:57, Kees Cook wrote:
> > On Thu, Sep 29, 2022 at 03:29:30PM -0700, Rick Edgecombe wrote:
> >> Shadow stack is supported on newer AMD processors, but the kernel
> >> implementation has not been tested on them. Prevent basic issues from
> >> showing up for normal users by disabling shadow stack on all CPUs except
> >> Intel until it has been tested. At which point the limitation should be
> >> removed.
> >>
> >> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> > So running the selftests on an AMD system is sufficient to drop this
> > patch?
> 
> Yes, that's enough.
> 
> I _thought_ the AMD folks provided some tested-by's at some point in the
> past.  But, maybe I'm confusing this for one of the other shared
> features.  Either way, I'm sure no tested-by's were dropped on purpose.
> 
> I'm sure Rick is eager to trim down his series and this would be a great
> patch to drop.  Does anyone want to make that easy for Rick?
> 
> <hint> <hint>

Hey Gustavo, Nathan, or Nick! I know y'all have some fancy AMD testing
rigs. Got a moment to spin up this series and run the selftests? :)

-- 
Kees Cook