From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AD11A1C3BF7; Tue, 11 Feb 2025 02:25:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739240758; cv=none; b=tTDPw8N0u4yqvA0YkrSL8nLUC+sssXgLg715p7MzKH8ffIo7aqZsp2CJACVh3WxEgzBWKDiHUXAgCEqy0cZ/W7Vi88c9R9bhNYTBkJjlb3JWtNPcDnAGuH7NZSOXA0achB/rZuTLG4QJGxsK7d2cN/VPqdqc7dcZwDeiPSuyWTw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739240758; c=relaxed/simple; bh=fCEiqwoA3v7oU0TSGkHZY1bVzz2hw5uBTMk7/MFmurs=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=Adq6WGlM5q5drVApP+YSjGV0jwyUGJEfBPXQfqBUViwDqrhQ3skQUv1vRS0Uyxh77wwVZJzUDZYXpuqcvXwjUAEtyX3MI9JoBXBjCWGRwWpFJasGpdsmqm+w1umhwk9P9E78n0kgz4Rsz5ARWxrZMpyFVU6W8fgwM8dETTu2RCc= ARC-Authentication-Results:i=1; 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h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=TbEGg/yha9wWptg/E8hA7g1U0OWlhbrtcPEtfdt/7m36tQPYiUhqMFoVM4KDepir4 JdrolLES+w/NycmFwshLplnsnkchVMHSWzMGnoqHH1Sdri288Hl5aRpFY7kpSO+6JG cPQdoGsEsf7mdokA7Uej767pKhlaTSBbI6gVfOmUkNT2L1UtyXwFKOEWnnFyXJE5BS B1uI5aEK5mpBjuN7vG7kTnImyyzo6jPDT8fs3FZrcjybgpMNjFDFHNSYPTd/I5NZih Az36LZW/l1ZPjnZVq6E/JP9r0ZqGopWamTKJ2TdTeazH5M0RJFPHmwm8aO6B+Pw5Aq juec7HcVTzQwg== Message-ID: <88ba8736-52b8-470c-ba5d-56c1cc5f5b8b@zytor.com> Date: Mon, 10 Feb 2025 18:25:01 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 0/5] x86/cpufeatures: Automatically generate required and disabled feature masks From: Xin Li To: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, will@kernel.org, peterz@infradead.org, yury.norov@gmail.com, akpm@linux-foundation.org, acme@kernel.org, namhyung@kernel.org, brgerst@gmail.com, andrew.cooper3@citrix.com, nik.borisov@suse.com References: <20250106070727.3211006-1-xin@zytor.com> Content-Language: en-US Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/5/2025 11:07 PM, Xin Li (Intel) wrote: > The x86 build process first generates required and disabled feature > masks based on current build config, and then uses these generated > masks to compile the source code. When a CPU feature is not enabled > in a build config, e.g., when CONFIG_X86_FRED=n, its feature disable > flag, i.e., DISABLE_FRED, needs to be properly defined and added to > a specific disabled CPU features mask in , > as the following patch does: > https://lore.kernel.org/all/20231205105030.8698-8-xin3.li@intel.com/. > As a result, the FRED feature bit is surely cleared in the generated > kernel binary when CONFIG_X86_FRED=n. > > Recently there is another case to repeat the same exercise for the > AMD SEV-SNP CPU feature: > https://lore.kernel.org/all/20240126041126.1927228-2-michael.roth@amd.com/. > https://lore.kernel.org/all/20240126041126.1927228-23-michael.roth@amd.com/. > > It was one thing when there were four of CPU feature masks, but with > over 20 it is going to cause mistakes, e.g., > https://lore.kernel.org/lkml/aaed79d5-d683-d1bc-7ba1-b33c8d6db618@suse.com/. > > We want to eliminate the stupidly repeated exercise to manually assign > features to CPU feature words through introducing an AWK script to > automatically generate a header with required and disabled CPU feature > masks based on current build config, and this patch set does that. > > Recently when working on the immediate form of MSR access instructions, > I needed to add a new CPU feature word for CPUID.7.1.ECX, and I had to > replace the same check "(NCAPINTS != 22)" with (NCAPINTS != 23) in 3 > different files as > https://github.com/xinli-intel/linux-fred-public/commit/aa80536927fcd293be8ae54e1d5e4d886cf83f21 > Obviously these replacements could be saved if the patch to add a new > CPU feature word is reworked on top of this patch set. > > So this seems a good opportunity to demonstrate the convenience out of > this patch set, and here comes v5 with just one more patch on top of v4 > that adds a new CPU feature word for CPUID.7.1.ECX and uses it for the > immediate form of MSR access feature. > > Link to v4: > https://lore.kernel.org/lkml/20240628174544.3118826-1-xin@zytor.com/ The patch proposed in the following review reminds me this infra improvement patch set again, so a gentle ping :) https://lore.kernel.org/lkml/CA+i-1C3LDJTf26WdBo7MvCdTs-dybqsUp3Ze7NowcOUHPWMXrg@mail.gmail.com/ Thanks! Xin