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Thu, 5 Dec 2024 05:10:01 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Thu, 05 Dec 2024 11:09:41 +0100 From: "Arnd Bergmann" To: "Andy Shevchenko" , "Linus Torvalds" Cc: "Arnd Bergmann" , linux-kernel@vger.kernel.org, x86@kernel.org, "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Dave Hansen" , "H. Peter Anvin" , "Matthew Wilcox" , "Sean Christopherson" , "Davide Ciminaghi" , "Paolo Bonzini" , kvm@vger.kernel.org Message-Id: <74e8e9c6-8205-413a-97a4-aae32042c019@app.fastmail.com> In-Reply-To: References: <20241204103042.1904639-1-arnd@kernel.org> <20241204103042.1904639-10-arnd@kernel.org> Subject: Re: [PATCH 09/11] x86: rework CONFIG_GENERIC_CPU compiler flags Content-Type: text/plain Content-Transfer-Encoding: 7bit On Thu, Dec 5, 2024, at 09:13, Andy Shevchenko wrote: > On Wed, Dec 04, 2024 at 03:33:19PM -0800, Linus Torvalds wrote: >> On Wed, 4 Dec 2024 at 11:44, Arnd Bergmann wrote: > > ... > >> Will that work when you cross-compile? No. Do we care? Also no. It's >> basically a simple "you want to optimize for your own local machine" >> switch. > > Maybe it's okay for 64-bit machines, but for cross-compiling for 32-bit on > 64-bit. I dunno what '-march=native -m32' (or equivalent) will give in such > cases. >From the compiler's perspective this is nothing special, it just builds a 32-bit binary that can use any instruction supported in 32-bit mode of that 64-bit CPU, the same as the 32-bit CONFIG_MCORE2 option that I disallow in patch 04/11. Arnd