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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 BD2BBC88E73 for ; Tue, 15 Sep 2026 08:43:57 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.1421531.1647330 (Exim 4.92) (envelope-from ) id 1x6OlV-0001xu-IS; Tue, 15 Sep 2026 08:43:45 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 1421531.1647330; Tue, 15 Sep 2026 08:43:45 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1x6OlV-0001xn-F1; Tue, 15 Sep 2026 08:43:45 +0000 Received: by outflank-mailman (input) for mailman id 1421531; Tue, 15 Sep 2026 08:43:44 +0000 Received: from mx.expurgate.net ([195.190.135.10]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1x6OlU-0001xh-2p for xen-devel@lists.xenproject.org; Tue, 15 Sep 2026 08:43:44 +0000 Received: from mx.expurgate.net (helo=localhost) by mx.expurgate.net with esmtp id 1x6OlS-00BQwV-MU for xen-devel@lists.xenproject.org; Tue, 15 Sep 2026 10:43:42 +0200 Received: from [10.42.69.11] (helo=localhost) by localhost with ESMTP (eXpurgate MTA 0.9.1) (envelope-from ) id 6aa90535-8faa-0a2a0a5109dd-0a2a450bd286-40 for ; Tue, 15 Sep 2026 10:43:42 +0200 Received: from [74.125.225.140] (helo=mail-wm2-f12.google.com) by tlsNG-42698a.mxtls.expurgate.net with ESMTPS (eXpurgate 4.57.1) (envelope-from ) id 6aa9053e-b7e8-0a2a450b0019-4a7de18c9bde-3 for ; Tue, 15 Sep 2026 10:43:42 +0200 Received: by mail-wm2-f12.google.com with SMTP id 5b1f17b1804b1-49ccfd61ecaso27918485e9.3 for ; Tue, 15 Sep 2026 01:43:42 -0700 (PDT) Received: from pumpkin (82-69-66-36.dsl.in-addr.zen.co.uk. [82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49e7ef24be2sm30342585e9.0.2026.09.15.01.43.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Sep 2026 01:43:41 -0700 (PDT) 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" Authentication-Results: eu.smtp.expurgate.cloud; dkim=pass header.s=20251104 header.d=gmail.com header.i="@gmail.com" header.h="Content-Transfer-Encoding:Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Subject:Cc:To:From:Date" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789461822; x=1790066622; darn=lists.xenproject.org; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=wn/lyeTbbPBDsoxu3rQlBRh1hn3vc28DqPKEKt99NCc=; b=cLZ1/oxtvB5c8AAMWRFeVIFWMKniREzNFe5Jgp/GISC+m3rFDLOsGQGSVJ6OoYel2K Ph/lIZo+GYkIhUt07jW4baHRga6sIcovszvq0opSIIOAJEeT0Q/bfj1lE1wJCVTGrm0w oLeMT4onH89E5y/rdGLZRHumsM+3OKBEp4Eq/OMIsX9Ycspdf/1KFpNc4D9M9oeiimvI YiZ6M0fM1VXN2w+f1ydchwqJp85B9JFPK7IdnWa93pG/59t1QgTDT/mqty3COcawfPPw HgYH+0xWlq4a2DZsxPEcyM0lsSvVrEQ33pw6+qfHmljUBiG7augE+8hsHOG6OUbQkRwo Wg6g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789461822; x=1790066622; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=wn/lyeTbbPBDsoxu3rQlBRh1hn3vc28DqPKEKt99NCc=; b=EaSP7pG4YUu/qXeocyWVvOrDatsX8rvyFCdm95B6Hs6BaEaZEXpJVrDEg901kdrAPG +OMgnJrl00ZZAjO2tt8cZsQaUpewrrSXMWzcM8IMZQFUEFIg/AU8txGCaacfC3KzH99W XbzygWJl7CITd8Kd81spCSPwaIfKx/vR4NMBJ2NFjFfU0MyExtvXj5ROz19kESNn7wVQ i0eQssNioF6dTjO/UYz1FwST1VM7T/pKxiiuaP7qm0/kXgpejYs69G3+DQKDVNNPutVY QiDAv/JNDxSp0dJ/BzRLan7KPPwqQYhtSYo8SOQ0FiIrKWYch5RK74yP7pbBrtRyi0aZ Xlrw== X-Forwarded-Encrypted: i=1; AKwUvBwbF9X5ZmazQaYRh9Zbbszt3MPuOUmMbI1v2hkO+nj5yjf6rjD+PZkVQSqwdFJUbHPaTV5NcpFb2jU=@lists.xenproject.org X-Gm-Message-State: AFuF++mMlf59VEffwhAnX3cWqqMyXLhpravtTyPp1QqIj4sUMlsfg9+W OO6nHxkKjK7CMyQdRmokpdqEfutF1R2+ac1Ccq3Jm3w5VBnOFUQRrNmA X-Gm-Gg: AYBFou0eNsUPV+E0JkrOS1ydsyXDZuuH/raf0JEAK+rJWmN6s91EUg4l/+Ux40sXzIT 1C/CVrh+i3ch7UqHR4BrUNlArGGExbLCn5vZEonGF5ctC8wMA37bXGeeGr9GKlafrAEETOMwMHA nfz0PsWJdHFZNsyOKtg3XsImFKdKil+OtIGdlB8PGp10B3V4OMTfcoXy7mK6sixe2XqJQpLMl7x tJ04QJt5FcP+OiCguTA6ntZys+mxJdTg4lYksqG5Wp8MPQTr9KlAmzd8KchKN+u8hlCRHANT0kT HiHjrsefU0qaaLQYBQNfa8RNmZE8NDB2hi35IJEIo7FiHDFhy/2ky44D4up3dOpbT4NblITKrP4 2BjzgWBKrTEgIhyVrolkZn7W+TVwmVsEreNJv9Ib7OlAda2FiW4YhGHL/ZMm61TNha88J5rU37X 9dIcS+kYZAZGYb6tO6rpdSWFsloYE6Zq3ZmptVgW+zIIgJ8TGGxypq1FO2Vo0bi87vFWQMvhymz sk8JC3cCu8PRLHkADDDkEK4stE5kSkCGv+o X-Received: by 2002:a05:600c:3593:b0:49c:e3ad:41d3 with SMTP id 5b1f17b1804b1-49e7a5edc17mr72558105e9.0.1789461821804; Tue, 15 Sep 2026 01:43:41 -0700 (PDT) Date: Tue, 15 Sep 2026 09:43:39 +0100 From: David Laight To: Borislav Petkov Cc: Mauricio Faria de Oliveira , Thomas Gleixner , Ingo Molnar , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Juergen Gross , Alexey Dobriyan , Boris Ostrovsky , Jan Beulich , Brian Gerst , kernel-dev@igalia.com, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org Subject: Re: [PATCH v9 4/5] x86/cpuid: fix unbootable VMs by really inlining memcmp() in hypervisor_cpuid_base() Message-ID: <20260915094339.39a83b54@pumpkin> In-Reply-To: <20260915051155.GGaqjTm7yIluwxZ80x@fat_crate.local> References: <20260822-pvh-kasan-inline-v9-0-e70ef3b75b6a@igalia.com> <20260822-pvh-kasan-inline-v9-4-e70ef3b75b6a@igalia.com> <20260911043822.GHaqOFvnw5mQ0s89QQ@fat_crate.local> <6113f06c790cfe1141d2dc09b68937b6@igalia.com> <20260915051155.GGaqjTm7yIluwxZ80x@fat_crate.local> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-purgate-ID: tlsNG-42698a/1789461822-A90CD9EA-CE4605F9/0/0 X-purgate-type: clean X-purgate-size: 773 On Mon, 14 Sep 2026 22:11:55 -0700 Borislav Petkov wrote: > On Mon, Sep 14, 2026 at 08:22:08AM -0300, Mauricio Faria de Oliveira wrote: > > In the review of the original patchset (fixed by this series) it is > > mentioned that a compiler might turn it into a memcmp() [1] -- and thus > > revert back to the same issue. > > > > [1] https://lore.kernel.org/all/877ccz12ab.ffs@tglx/ > > Hmm, never heard that before but that doesn't mean anything. Probably should > mention it in one of the commit messages so that we know for the future... > It definitely has a habit of converting copy loops to memcpy(). Annoying when they are short. But usually easily avoidable by sprinkling 'volatile' or barrier() in the right places. David