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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-46c1ee01c3bsm23853241f8f.10.2026.06.26.00.41.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jun 2026 00:41:14 -0700 (PDT) Date: Fri, 26 Jun 2026 08:41:13 +0100 From: David Laight To: Eric Biggers Cc: x86@kernel.org, linux-um@lists.infradead.org, linux-raid@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , Andrew Morton Subject: Re: [PATCH 2/8] um: Check for missing AVX and AVX-512 xstate bits Message-ID: <20260626084113.42eae31c@pumpkin> In-Reply-To: <20260626043731.319287-3-ebiggers@kernel.org> References: <20260626043731.319287-1-ebiggers@kernel.org> <20260626043731.319287-3-ebiggers@kernel.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 25 Jun 2026 21:37:25 -0700 Eric Biggers wrote: > If the CPU declares AVX or AVX-512 support, verify that all the > corresponding xstate bits are also set. If any are missing, warn and > don't set the corresponding X86_FEATURE_* flags. > > This eliminates the perceived need for UML-supporting AVX and AVX-512 > optimized code in the kernel (that is, lib/raid/ currently) to start > checking the xstate bits in addition to X86_FEATURE_AVX*. > ... > static void __init parse_host_cpu_flags(char *line) > { > + u64 xcr0 = read_xcr0(); > int i; > + > for (i = 0; i < 32*NCAPINTS; i++) { > if ((x86_cap_flags[i] != NULL) && strstr(line, x86_cap_flags[i])) 'line' comes from /proc/cpuinfo Surely something would be terribly wrong if that included something the kernel had disabled (or didn't support). David > - set_cpu_cap(&boot_cpu_data, i); > + validate_and_set_cpu_cap(i, xcr0); > } > } > > static void __init parse_cache_line(char *line) > {