From nobody Fri Oct 31 04:18:55 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass(p=reject dis=none) header.from=citrix.com ARC-Seal: i=1; a=rsa-sha256; t=1751467307; cv=none; d=zohomail.com; s=zohoarc; b=NU7hv2JihpaTt+v1aB5MJClB6/74dFt8rt+ppH7rldWFRlOMiqtRDB/3z524s7zc/Rej5oYDkmNI6LUvValM52cBu1F90O5tXLWVLl7YBQi0XeKk7V0ahii42RoTRBz+mnErRHwlpUoIMxX4FCJQwvvhEWLZ2XCJanZUbMe6fCE= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1751467307; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=nxIVNczZ1rIA2YAlLtpWMc3jJY/ZNCuwxwnSmoLdJTc=; b=NnBMZtNl2dD6DZ9dnF70E096u0qToXhDy1sRIqdu3eGnikpzUfN4zYM/FH+xf6WEjl7gCwGyaCwEwjtnzMnjvHt+sxdb9Qo1TkF/sIwfsYb4H+g+lsO4A/Eb+XQfwcwcrnqqUR34y2BPH4DQDisuUi5YAicUI0aec7fdVoUS79s= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass header.from= (p=reject dis=none) Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1751467307667839.6983298611775; Wed, 2 Jul 2025 07:41:47 -0700 (PDT) Received: from list by lists.xenproject.org with outflank-mailman.1031267.1405071 (Exim 4.92) (envelope-from ) id 1uWyeU-0000FO-Sd; Wed, 02 Jul 2025 14:41:34 +0000 Received: by outflank-mailman (output) from mailman id 1031267.1405071; Wed, 02 Jul 2025 14:41:34 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1uWyeU-0000Dt-JD; Wed, 02 Jul 2025 14:41:34 +0000 Received: by outflank-mailman (input) for mailman id 1031267; Wed, 02 Jul 2025 14:41:33 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1uWyeT-0007qI-OW for xen-devel@lists.xenproject.org; Wed, 02 Jul 2025 14:41:33 +0000 Received: from mail-wm1-x334.google.com (mail-wm1-x334.google.com [2a00:1450:4864:20::334]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id a54f0113-5752-11f0-b894-0df219b8e170; Wed, 02 Jul 2025 16:41:32 +0200 (CEST) Received: by mail-wm1-x334.google.com with SMTP id 5b1f17b1804b1-4537fdec39fso15338115e9.0 for ; Wed, 02 Jul 2025 07:41:32 -0700 (PDT) Received: from localhost.localdomain (host-92-26-98-202.as13285.net. [92.26.98.202]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-453823ad20bsm230946905e9.20.2025.07.02.07.41.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Jul 2025 07:41:30 -0700 (PDT) X-Outflank-Mailman: Message body and most headers restored to incoming version X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: a54f0113-5752-11f0-b894-0df219b8e170 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1751467291; x=1752072091; darn=lists.xenproject.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=nxIVNczZ1rIA2YAlLtpWMc3jJY/ZNCuwxwnSmoLdJTc=; b=QQs/R/gGg5vFfbmPazfAM/w8sqCZAiENDbj2vwNdOMM4xoi5cNLbP1DgEZ/9zzIdYJ 3GJlscCOdHW0s7wlht2WPjRavKRuasUNDJn1m1X/Fq7FxUMf3qLrG3QssXA8LjboPAUe guZCxMWmY9cOx4h6r6nfhelGfW977PFze6ZDI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1751467291; x=1752072091; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=nxIVNczZ1rIA2YAlLtpWMc3jJY/ZNCuwxwnSmoLdJTc=; b=TZ36NIQI092IIikwIrMVBSGhh5NFyNa+rk3dRmbZ737rCorFTWzZ8onDQi5wyI/5Yd UUWz571GgaWACFw9ne8EtjIfnJfjU/Qhpn9Tcd9PKCqHogiFg2mpedfg92giYw87q2jf r9np3U/flCIQu+g39FMS1/EUXvtuvEPiC+mwqxVO3NsvOE2nSykM5EhktOtnoMiX7UXl rWUkTmYYARUghf40vuxytH4mk6Z/nD1E80lWK0DQ5x6ivlqjKJ2nwEwHvaueCIop5Dcq Abf3zysOg/IX3joD0bJcF46dqA49q4WQwJRCXJg/cpg8iures6kt1SJkiBm3pX/1OjDg RRyw== X-Gm-Message-State: AOJu0Yxgi2+jTV4fNJZSnVujY1m5GZEQ5T5czoLiZkqdbvCAnk8HrGP4 145Bd2jYdx8IZKgi8A/nyBbvh3LCE9EUXr5yufnQluweJUcGxTWYRQeRLYz2/2/hZsbZNEsPrDM M+v7lNk+t4w== X-Gm-Gg: ASbGncuWYWR37A/ELPrnyv+1kzeGDo6jyYSh20Tu2Bb6EmgRmu8ts58jZZ+iYCefOZC jQx7LHQeYFgenbG4TTroTqiESpOhh6sbmciOzPogj5fhe2bWJvRzOOsiSSdGNfVLb4GRnh+31As hQehj24Xz9BOnCapAM/FpxMubqR0gUfI2VUSP5Db5xPRMcPzxxuuoxXTfp43eozEi+SP6DypSyw e5deM6mt5qahLBj4gG7SVoc9pdK62LnVBpfay6qaAgwP31QtlZZkzf16PfTYUkILTA8kbn/gXH3 YSak9JuEu/1OynpavCjUUM6irLuFcIg21ISISiAYOZ7nQPcquzaAR7QlfnWYvX2g31ymHWCODMU /Jkt6smNhWIAtuMVINlj2oXkwhRjC6eBjzqwFVSZXVQRWRA== X-Google-Smtp-Source: AGHT+IHPfekVRNza1oHlHHApBPWw80wB98FcLF5N54CE2FrBTKMCr5qBmn3s7N87TlH53I2ia8v4cA== X-Received: by 2002:a05:600c:1d1a:b0:442:dc6f:2f11 with SMTP id 5b1f17b1804b1-454a372e257mr30396825e9.25.1751467291320; Wed, 02 Jul 2025 07:41:31 -0700 (PDT) From: Andrew Cooper To: Xen-devel Cc: Andrew Cooper , Jan Beulich , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Anthony PERARD , Michal Orzel , Julien Grall , Stefano Stabellini Subject: [PATCH 5/6] x86/idle: Drop incorrect smp_mb() in mwait_idle_with_hints() Date: Wed, 2 Jul 2025 15:41:20 +0100 Message-Id: <20250702144121.1096448-6-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250702144121.1096448-1-andrew.cooper3@citrix.com> References: <20250702144121.1096448-1-andrew.cooper3@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @citrix.com) X-ZM-MESSAGEID: 1751467308472116600 With the recent simplifications, it becomes obvious that smp_mb() isn't the right barrier; all we need is a compiler barrier. Include this in monitor() itself, along with an explantion. No functional change. Signed-off-by: Andrew Cooper --- CC: Jan Beulich CC: Roger Pau Monn=C3=A9 CC: Anthony PERARD CC: Michal Orzel CC: Julien Grall CC: Stefano Stabellini --- xen/arch/x86/acpi/cpu_idle.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c index 13040ef467a0..de020dfee87f 100644 --- a/xen/arch/x86/acpi/cpu_idle.c +++ b/xen/arch/x86/acpi/cpu_idle.c @@ -66,8 +66,12 @@ static always_inline void monitor( alternative_input("", "clflush (%[addr])", X86_BUG_CLFLUSH_MONITOR, [addr] "a" (addr)); =20 + /* + * The memory clobber is a compiler barrier. Subseqeunt reads from the + * monitored cacheline must not be hoisted over MONITOR. + */ asm volatile ( "monitor" - :: "a" (addr), "c" (ecx), "d" (edx) ); + :: "a" (addr), "c" (ecx), "d" (edx) : "memory" ); } =20 static always_inline void mwait(unsigned int eax, unsigned int ecx) @@ -456,7 +460,6 @@ void mwait_idle_with_hints(unsigned int eax, unsigned i= nt ecx) [in_mwait] "=3Dm" (stat->in_mwait)); =20 monitor(this_softirq_pending, 0, 0); - smp_mb(); =20 if ( !*this_softirq_pending ) { --=20 2.39.5