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Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] x86/cpu/centaur: Disable X86_FEATURE_FSGSBASE on Zhaoxin C4600 Message-ID: References: <20260228173704.62460-1-me@ziyao.cc> <72356849-27d0-46c7-b659-c1a3b260de8c@intel.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <72356849-27d0-46c7-b659-c1a3b260de8c@intel.com> X-ZohoMailClient: External On Sat, Feb 28, 2026 at 04:33:18PM -0800, Dave Hansen wrote: > On 2/28/26 09:37, Yao Zi wrote: > > Let's disable the feature on this problematic CPU and warn the user > > about the quirk. x86_model_id is used to match the platform to avoid > > unexpectedly breaking other CentaurHauls cores with conflicting > > family/model ID. > > Wait a sec. There are lots of different microarchitectures with the same > family/model and no other way to identify them but the model id string? > > We've used string in a handful of places, but it's an absolute last > resort. Are you *sure* there's no stepping or anything? No. The commit message should be more clear, I have no clue that there are other designs with the same family/model/stepping combination. However, C4600 is a design from Zhaoxin instead of VIA but using CentaurHauls as vendor ID, thus conflicts may happen since they're different entities. So I take the safest way. > I kinda think we should keep this like all the other vendors and keep it > to model/family/stepping. If the vendor has grouped too many > non-vulnerable CPUs under that, then ... this is going to be a good > learning to bring back to the CPU design team. > > If you're changing the CPU in a way that it's possible to regress > things, you *need* to bump the model or stepping. Period. If you don't, > the baby might get thrown out with the bathwater. > > Please resend this with a normal x86_match_cpu() and x86_cpu_id[] array. The concerns may be too farsight as there's no clue indicating conflicts actually happened. I'll take the change in v2 if you still think it's appropriate. Regards, Yao Zi