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[91.219.240.8]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42e902b681esm20158575e9.37.2024.09.24.05.04.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Sep 2024 05:04:05 -0700 (PDT) From: Vitaly Kuznetsov To: David Laight Cc: Jan Richter , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , Paolo Bonzini , Sean Christopherson Subject: RE: [PATCH] KVM: selftests: x86: Avoid using SSE/AVX instructions In-Reply-To: <2a62086810c14d0e88e38706a06aedde@AcuMS.aculab.com> References: <20240920154422.2890096-1-vkuznets@redhat.com> <2a62086810c14d0e88e38706a06aedde@AcuMS.aculab.com> Date: Tue, 24 Sep 2024 14:04:04 +0200 Message-ID: <87ikull0ln.fsf@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain David Laight writes: > From: Vitaly Kuznetsov >> Sent: 20 September 2024 16:44 >> >> Some distros switched gcc to '-march=x86-64-v3' by default and while it's >> hard to find a CPU which doesn't support it today, > > I didn't think that any of the Atom based cpu supported AVX. > I'm pretty sure one we use that are still in production as > server motherboards don't support it. > > Doesn't -v3 also require support for the VEX encoding. > Which removes a lot of perfectly reasonable cpu? > Well, distros making such decision are obviously not very interested in running on these CPUs then :-) In this particular case, the distro was Centos Stream 10 and they are very explicit about the decision: https://developers.redhat.com/articles/2024/01/02/exploring-x86-64-v3-red-hat-enterprise-linux-10#new_cpu_capabilities_in_x86_64_v3 and 'gcc -v' tells me Configured with: ../configure ... --with-arch_64=x86-64-v3 ... ... gcc version 14.2.1 20240801 (Red Hat 14.2.1-1) (GCC) -- Vitaly