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 30FFB2391AD; Wed, 4 Dec 2024 17:56:40 +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=1733335003; cv=none; b=l6VWyhwuiblJI5nvOp57jZ+ptP7el8RtpHuttBDWg5YqTJ01vqP6+uvN0MQyvDGDX74lAvStSS8FxactWoslx8KjmwGENTLWnu5cM/hMCT1ZvX2HBT5OAMl6xaycUtKag8knv3Jlp4eARrLmzNxMSDzV2gLQeAXlQtZRmTc/aLM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733335003; c=relaxed/simple; bh=eqMyNIsN1uT5Xpv2zdcqbksS85BUsOtJ32KdNLU1I0U=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=oMfRAexDJhbF8ohsQKMMLKG2fglTQZ39GfddJHf7gj8hbPEjRbIhAQhO2QYstyeBwqfCcouJzfk0hvZmv0WVPrGXJZo0Mi7m/Zxjl6jNNoECT0zMmZRnI1Hd3yj0lQ6PPvXQs0eSMfG262RAoOdkKMK06ERZ6GHxJHADf2haTrk= ARC-Authentication-Results:i=1; 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h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=EdNz09I5sLH7fW5kPPKAD247aZDUOBUyGT2Su2dVsBmPC1bNO4c5Rd8lrqXYzNkUI mE2QCgM+ARHlxSp+NlGLtLZTl0Z/4aF8bygTRcpiDSGNEau7skDUXw9XZfzvdoRDHp RdDFkFEQd/BQj6DaUiocpEw6qHuIM7fy24VpBMqIUDQHYHhxiiJa5G/vR8nxyUX4HC wSIIjThDlQRzR+MIAljT7S8fU02HdDNGfrqlI4GLmRnUETHToYxk2mUQ6/m1Dv6Fcw W2vO3KFsQAbZGg6WL5tbr+rPDv+tZPRr3PY/OHRVQKMfpDKXePAph4Kw8vU5y6JbD2 bEy2YRBbaNA0Q== Message-ID: <308cddef-9efa-47ab-b499-34c52480dd09@zytor.com> Date: Wed, 4 Dec 2024 09:56:02 -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 v4 0/4] 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, akpm@linux-foundation.org, acme@kernel.org, namhyung@kernel.org, brgerst@gmail.com, andrew.cooper3@citrix.com, nik.borisov@suse.com References: <20240628174544.3118826-1-xin@zytor.com> <23b9e88b-9d3b-4c34-a243-232ca2f53527@zytor.com> Content-Language: en-US Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 8/19/2024 11:25 PM, Xin Li wrote: > On 6/28/2024 10:45 AM, 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. >> >> Link to v3: >> https://lore.kernel.org/lkml/20240622171435.3725548-1-xin@zytor.com/ >> >> Changes since v3: >> * Add a few high-level comments to the AWK script (Nikolay Borisov). >> * Use '1U' instead of '1' in feature mask shifting (Andrew Cooper). >> * Checking NCAPINTS isn't necessary anymore.  It was needed when these >>    macros had to be manually updated, but now if cpufeatures.h changes >>    this header will be regenerated (Brian Gerst). >> * Enforce CPU feature mask values to be unsigned. >> >> Changes since v2: >> * Remove AWK code that generates extra debugging comments (Brian Gerst). >> * Move SSE_MASK to verify_cpu.S, the only place it is used (Brian Gerst). >> * Add a patch to generate macros {REQUIRED|DISABLED}_MASK_BIT_SET in the >>    new AWK script (Brian Gerst). >> >> Changes since v1: >> * Keep the X86_{REQUIRED,DISABLED}_FEATURE_ prefixes solely in >>    arch/x86/Kconfig.cpufeatures (Borislav Petkov). >> * Explain how config option names X86_{REQUIRED,DISABLED}_FEATURE_ >>    are formed (Borislav Petkov). >> * Remove code generating unused macros {REQUIRED,DISABLED}_FEATURE(x) >>    to tell if a CPU feature, e.g., X86_FEATURE_FRED, is a required or >>    disabled feature for this particular compile-time configuration. >> > > A gentle ping... > Another ping!