From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 27D23606A31A for ; Tue, 20 Oct 2026 01:15:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=KQFOTWLR; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XsPEwVCY 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=SrYg+4IxYYwBTzHh7PTz0/BsfWinhw4uhwnWLlCjA3c=; b=KQFOTWLRopJhH0U5/9Vqmzev4Z yyItaUwrHSj9Z3Tga2h13IsEsYjfmI20GIsfA2GIWFPh/dG92uafaYnC2ATAOpGV8tUFOUkuhkeyM jx4xIeLHQAYL0FAOhUT0eryvq/bFaZP0io3C8T4GG4kpbOkN1h27FYIIjfSpoi7FdPS5mW2X8Jcmq IYaI82gLcaid/vmy0t3lksKSPe0otIdxq0dFAZzRiU5whFpX/2XGOuwAFlyRyaDvyN6llhnRiTGT+ idEmVB8TyHrgst8pQc4NN1Xnscz4rVYU1+PHjvROlcUhLHyZ4akZ5gO4m4a0lZhqkPDACa1TUf+Ts sGPtKouA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xIySA-00000008bHQ-2lVK; Tue, 20 Oct 2026 01:15:46 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xIyS9-00000008bHJ-33fG for kexec@lists.infradead.org; Tue, 20 Oct 2026 01:15:45 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 644A260098; Tue, 20 Oct 2026 01:15:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8CAB1F000C4; Tue, 20 Oct 2026 01:15:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792458944; bh=SrYg+4IxYYwBTzHh7PTz0/BsfWinhw4uhwnWLlCjA3c=; h=From:Subject:Reply-To:To:In-Reply-To:References:Date; b=XsPEwVCYnNTEG89vLNC+f/KM1ivegM8emhaoX9lGdQ4zqkwSClS7xFVRQ4Lo0BL16 Lkce1/tdnIWljMY9rQCxUsg0CixVgBbV3UwUPB3ochiNeSHyuvpzRZSj1Zt6s4GMdY DoR5BneRdAATusGwJvS8hRzLF1agwW17xpN4x+7kkM7E9bbZhEORWKNmG80o5IikmP ZK+SMha/hvBDsd5VGDgaJ7Ukg07spk2dHMXK/Z8LQPBlgrRtPfOLXyCurok0B9cOMf /GxGSDMyvKPp1nQuE4QfQAcB5nOrvu9ypJxZ+x2EPEn6VE9tYoBSX9iRq0NFowLs+s Lx818b2r10Dkg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 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, jpoimboe@kernel.org, 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, 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, blum@kernel.org, longman@redhat.com, bsegall@google.com In-Reply-To: <20261019011446.834487-2-pasha.tatashin@soleen.com> References: <20261019011446.834487-1-pasha.tatashin@soleen.com> <20261019011446.834487-2-pasha.tatashin@soleen.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 20 Oct 2026 01:15:41 +0000 X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "kexec" X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: > 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. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261019011446.8344= 87-1-pasha.tatashin@soleen.com?part=3D1