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 C0EEA2A1B2; Tue, 20 Aug 2024 06:26:20 +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=1724135183; cv=none; b=Def0CwwfjonbI0fYWnTR+vTSJ162hFcqpRNR6QIuuRGoSQ3rRX7y3+tWIyHyYbD5kELuNDsDaHT/Ukz75RA9ue+s5eB+MsLaEDAk58ZpWMUpklNz75ReKFOr9zsFPLI4HEYI4P/aP8gGxn+H/iFC5GU1JlGbmBClD8jxK6HB6ss= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724135183; c=relaxed/simple; bh=EZqc+00fgRRrEC4Xf7joFqSZzq2p9IEziTklnKWVHQU=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=ezzobHz57/lRMfjCLaQNSoL8nNlOZ03/XJw/fmh5CuK83nrpknlqwgg6TPlqAkyVu3ARgoBFiMO7ytfvupIPc4FUAmzQN7TqluhrCTf88uxRNxzN+aGGeI6cj+khq/OmM63bkUThhNf7xuVdMaP8/dJJBpUBAVHEnjv+quTwefY= ARC-Authentication-Results:i=1; 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h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=D/6Y8OiTNzjIp70nymc7pWQduoyXtY2bHPbNJeqx8lvge9gWjETD+Mwu/DuE42R8g d5nFb4civvTUK8rLi/4pj9m8MzKy15KeqtfSDJv1lw3Mw4xBLQQu+fqHl6z1GL6jpt 5JmSJTnwfEL/IB1cl9n8h7kILxXE25p4Z4ERPSHBfDGeKHUZ0ZgIRqvDJH4PVWbpPW 1c8N8v99xolCQfBmoBmPnEgocHzVV4dKxFm2y6myIpIGsBQP0vgy7TANSSQT1Gcyr9 tNuCPnuTjoSHDesMmEGpnFSqGGiWJjiMl16po9QDiU7waq90RUPlfnZmfAAbMEcn7V UC2tEeG/wsleQ== Message-ID: <23b9e88b-9d3b-4c34-a243-232ca2f53527@zytor.com> Date: Mon, 19 Aug 2024 23:25:17 -0700 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> Content-Language: en-US Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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...