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Mon, 9 Nov 2026 05:25:01 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-ThreadId: AqNyIDC2Pk_N Date: Mon, 09 Nov 2026 11:24:10 +0100 From: "Arnd Bergmann" To: "David Laight" , "Arnd Bergmann" Cc: "Ingo Molnar" , "Richard Weinberger" , "Anton Ivanov" , "Johannes Berg" , "Thomas Gleixner" , "Borislav Petkov" , "Dave Hansen" , "H. Peter Anvin" , "Peter Zijlstra" , "Will Deacon" , "Boqun Feng" , "Gary Guo" , "Yury Norov" , "Rasmus Villemoes" , "Boris Ostrovsky" , "Alexander Usyskin" , "Anthony L Nguyen" , "Przemek Kitszel" , x86@kernel.org, linux-kernel@vger.kernel.org, linux-um@lists.infradead.org Message-Id: In-Reply-To: <20261108203042.7e36f15b@pumpkin> References: <20261105163440.2381661-1-arnd@kernel.org> <20261105163440.2381661-4-arnd@kernel.org> <20261108203042.7e36f15b@pumpkin> Subject: Re: [PATCH 3/7] x86: make CX8 usage unconditional Content-Type: text/plain Content-Transfer-Encoding: 7bit On Sun, Nov 8, 2026, at 21:30, David Laight wrote: > On Thu, 5 Nov 2026 17:34:34 +0100 > Arnd Bergmann wrote: > >> From: Arnd Bergmann >> >> All supported CPUs now provide the cmpxchg8b instruction, so remove >> all compile-time and runtime checks for its presence and the fallback >> implementation, to assume it just works. > > Is it worth doing a run-time check early on any (trying) to output > a message and fail to boot? I think the existing checks in arch/x86/boot/cpucheck.c should be enough here, as they cover all known pre-586 CPUs and anyone running some other CPU that we can't detect is already on their own. Arnd