From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4E34415B0EE; Fri, 29 Nov 2024 20:50:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732913460; cv=none; b=lEuHuVuaccExw9A58l9Pa3JAmJbvni7PfX9g3Np2jG2O0N+YWYH5jDtl+twGXxq2A0xRM0gwo55o6SjyyIX0sntMCfeoC08YPzOMqkiKezEoPv2fljL+c8gbmHrJF6b3BxtUnSnn0HAQZv7BrpKLZTbjQYLx4VWCKKRVxRbHrVY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732913460; c=relaxed/simple; bh=LOIG9BSpFHYM/td2BjZkDpvQk8mBag9BFkKQJT+AOOE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NozuePd+YIRcqVDzgcCAHXop97I5+VKpMKALZIOSZRgFR3zwtogmtWjbLpLasN6g45lLANfutAKd27YNm/FLk3RpIT5Z1olpmzsqfrxtyc26eVJIYnwA8QdRbsvZ4c4olojl0ca7c94Y7BgllqiLVsoNtHlFNdKsL1jxZCNTH5A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XLzKyGn0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XLzKyGn0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74D60C4CECF; Fri, 29 Nov 2024 20:50:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732913459; bh=LOIG9BSpFHYM/td2BjZkDpvQk8mBag9BFkKQJT+AOOE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XLzKyGn0jFczUi2xloW4pdvLTxUdILY1RjHGyKFp5RjbZ6HR5V5MhcqgUSiCXi5RY pXvu0rD8M3pOmEXlISxYPcq7z/m0PkLGPEEt5wPjVkzl4S3W/djtwhPxlFa7WB9ajS gWPE3BLUkJZUsNK6GUkIzDf5y0ryaMzhYZ6EikQ1ZV9NPTaYZqigLsBQXsOnlHGHFg Qiij+wk3pMoOIr5ZPBBj5Afqtn5KNcfh1o9JYnzdc++X0K06V/xYjQwEJkHOIs00Ku +kO72knUeMIfi4kTVJH3VCUpeax/27sjjI97MM5V64W9vaA3YrJIjR7bCpA6RbVyeK 3mbn2bdHoRa+A== Date: Fri, 29 Nov 2024 15:50:58 -0500 From: Sasha Levin To: Pavel Machek Cc: Borislav Petkov , linux-kernel@vger.kernel.org, stable@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, puwen@hygon.cn, seanjc@google.com, kim.phillips@amd.com, jmattson@google.com, babu.moger@amd.com, peterz@infradead.org, rick.p.edgecombe@intel.com, brgerst@gmail.com, ashok.raj@intel.com, mjguzik@gmail.com, jpoimboe@kernel.org, nik.borisov@suse.com, aik@amd.com, vegard.nossum@oracle.com, daniel.sneddon@linux.intel.com, acdunlap@google.com, Erwan Velu Subject: Re: [PATCH AUTOSEL 5.15 11/12] x86/barrier: Do not serialize MSR accesses on AMD Message-ID: References: <20240115232718.209642-1-sashal@kernel.org> <20240115232718.209642-11-sashal@kernel.org> <20241128115924.GAZ0hbHKsbtCixVqAe@fat_crate.local> <20241128164310.GCZ0idnhjpAV6wFWm6@fat_crate.local> 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; format=flowed Content-Disposition: inline In-Reply-To: On Fri, Nov 29, 2024 at 09:34:53PM +0100, Pavel Machek wrote: >On Fri 2024-11-29 08:38:48, Sasha Levin wrote: >> On Fri, Nov 29, 2024 at 10:45:48AM +0100, Pavel Machek wrote: >> > Hi! >> > >> > > > You've missed the 5.10 mail :) >> > > >> > > You mean in the flood? ;-P >> > > >> > > > Pavel objected to it so I've dropped it: https://lore.kernel.org/all/Zbli7QIGVFT8EtO4@sashalap/ >> > > >> > > So we're not backporting those anymore? But everything else? :-P >> > > >> > > And 5.15 has it already... >> > > >> > > Frankly, with the amount of stuff going into stable, I see no problem with >> > > backporting such patches. Especially if the people using stable kernels will >> > > end up backporting it themselves and thus multiply work. I.e., Erwan's case. >> > >> > Well, some people would prefer -stable to only contain fixes for >> > critical things, as documented. >> > >> > stable-kernel-rules.rst: >> > >> > - It must fix a problem that causes a build error (but not for things >> > marked CONFIG_BROKEN), an oops, a hang, data corruption, a real >> > security issue, or some "oh, that's not good" issue. In short, something >> > critical. >> > >> > Now, you are right that reality and documentation are not exactly >> > "aligned". I don't care much about which one is fixed, but I'd really >> > like them to match (because that's what our users expect). >> >> You should consider reading past the first bullet in that section :) >> >> - Serious issues as reported by a user of a distribution kernel may also >> be considered if they fix a notable performance or interactivity issue. >> >> It sounds like what's going on here, no? > >Is it? I'd not expect this to be visible in anything but >microbenchmarks. Do you have user reports hitting this? > >It is not like this makes kernel build 10% slower, is it? On Fri, Nov 29, 2024 at 10:30:11AM +0100, Erwan Velu wrote: >This patch greatly impacts servers on production with AMD systems that >have lasted since 5.11, having it backported really improves systems >performance. >Since this patch, I can share that our database team is no longer >paged during the night, that's a real noticeable impact. -- Thanks, Sasha