From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CDEEECC6B39 for ; Thu, 15 Oct 2026 15:41:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Reply-To:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Date: Content-Transfer-Encoding:Content-Type:References:In-Reply-To:To:Subject:From :Message-ID:Cc:MIME-Version:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=xfJErzoYwObujgAa/2qQszEg/7aBAMpYNTEs6++lwjo=; b=yp3IklQP0R/MoQYEaOfMJ536az S7ZRztfX3jS3di5YK5knqSGnw3dUbyyqn9fDmJZgNF4YpEp8KNDaNuoWUCfq99+ipSaCk+cQ0pK57 Ru9oX81QtZUiVsBUD5ZJkNo81DU/I4shvdmIcBvBAeDFpv9BjDtIN9Mv+Rot2QaiLpa94MW9YLXak 3S5qGC97ORWKc1lK9pLKb822siFk62NKnZ8h1FRqm5cUZkmYD11RsQ8cmFN+g2xcBl+YrUHe6KD2T zvX/8RtHjfJ/yozJIy8g6V0sREfLo5fKIz4EUF1+tA3DjtKrCStnKUScPvVHr56Dvj15XwuwxXgjX eBPTWzWA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xHNaB-00000000av5-27LJ; Thu, 15 Oct 2026 15:41:27 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xHNaA-00000000auP-1DNz for kexec@lists.infradead.org; Thu, 15 Oct 2026 15:41:26 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 1679460200; Thu, 15 Oct 2026 15:41:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE6F01F000C4; Thu, 15 Oct 2026 15:41:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792078884; bh=xfJErzoYwObujgAa/2qQszEg/7aBAMpYNTEs6++lwjo=; h=From:Subject:Reply-To:To:In-Reply-To:References:Date; b=Taa7q0qBqdNXT4iKTUtAbfULekNwY5CfK2ZbWyMcUBReHj+LYJFaT4d3yMtWaUb6M 3fSncbyc6au4HKylAkbL/nZL3ld/D1bHwDE0dO9nDD580KnKGw71FGdG2o779YZYlf RG84c2TVVojPHNBIju9Jg7Mjfqzd7ixbHFUtSqqbIO89gu/wrL3RrgQxN0T2xTxcBQ QePuXxGsop/5u+UvhcGX3KNDH9+AyN1Ys7ppPjKwgRctmGDeiLCKdAQC21IDlTGyIN /0BX72GHU3Z/2VR5XEl+yZiHTmzA82IsTA50iaXFEBfRxdkNRhBQhDwup+/65MwDRM uNetcaSInpTYg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v1 1/8] x86/realmode: Remove unnecessary WBINVD from AP startup trampoline To: "Pasha Tatashin" , kees@kernel.org, rppt@kernel.org, juri.lelli@redhat.com, nik.borisov@suse.com, tglx@kernel.org, vschneid@redhat.com, kprateek.nayak@amd.com, vincent.guittot@linaro.org, bp@alien8.de, thorsten.blum@linux.dev, tony.luck@intel.com, david@kernel.org, mingo@redhat.com, akpm@linux-foundation.org, seanjc@google.com, ljs@kernel.org, zhangguopeng@kylinos.cn, dietmar.eggemann@arm.com, mhocko@suse.com, vinicius.gomes@intel.com, tj@kernel.org, vbabka@kernel.org, peterz@infradead.org, surenb@google.com, hpa@zytor.com, x86@kernel.org, dmatlack@google.com, tim.c.chen@linux.intel.com, kexec@lists.infradead.org, pratyush@kernel.org, dave.hansen@linux.intel.com, rostedt@goodmis.org, gmonaco@redhat.com, jgross@suse.com, mgorman@suse.de, graf@amazon.com, liam@infradead.org, ridong.chen@linux.dev, longman@redhat.com, bsegall@google.com In-Reply-To: <20261015153331.1872641-2-pasha.tatashin@soleen.com> References: <20261015153331.1872641-1-pasha.tatashin@soleen.com> <20261015153331.1872641-2-pasha.tatashin@soleen.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 15 Oct 2026 15:41:22 +0000 X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org > trampoline_start executes WBINVD in 16-bit real mode before switching to > protected mode. This WBINVD was originally added in the 1990s for > Sequent NUMA-Q hardware (as noted by the comment in trampoline_32.S: > "Needed for NUMA-Q should be harmless for others"), whose cross-quad > caches came up non-coherent prior to OS initialization. Sequent NUMA-Q > support (CONFIG_X86_NUMAQ) was removed in commit b5660ba76b41 > ("x86, platforms: Remove NUMAQ"). >=20 > Per the Intel SDM (Vol. 3A, Table 10-1, note 2) and AMD APM, the INIT > IPI used to wake secondary CPUs preserves cache contents and leaves > CR0.CD and CR0.NW unchanged (0, as already enabled by firmware or the > kernel). Neither sev_es_trampoline_start nor trampoline_start64 > executes WBINVD. >=20 > On modern multi-core processors with large shared last-level caches > (such as 504 MB shared L3 per socket on Intel Xeon 6985P-C), WBINVD is > not harmless: each execution flushes and invalidates the entire > coherence domain's caches and takes ~85-115 ms per CPU while disturbing > active workloads on online CPUs. >=20 > Remove the obsolete WBINVD from trampoline_start. >=20 > 2-socket, 480-CPU Intel Xeon 6985P-C (N=3D479, mean of 10 runs): > Offline: 40.40 s -> 40.46 s > Online: 65.83 s -> 11.14 s (-83.1%) > Total: 106.23 s -> 51.60 s (-51.4%) >=20 > Signed-off-by: Pasha Tatashin Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261015153331.1872= 641-1-pasha.tatashin@soleen.com?part=3D1