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 2E5D5C3600C for ; Thu, 27 Mar 2025 08:22:04 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.928615.1331300 (Exim 4.92) (envelope-from ) id 1txiUu-0000kP-MW; Thu, 27 Mar 2025 08:21:56 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 928615.1331300; Thu, 27 Mar 2025 08:21:56 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1txiUu-0000kI-JB; Thu, 27 Mar 2025 08:21:56 +0000 Received: by outflank-mailman (input) for mailman id 928615; Thu, 27 Mar 2025 08:21:55 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1txiUt-0000iR-Mc for xen-devel@lists.xenproject.org; Thu, 27 Mar 2025 08:21:55 +0000 Received: from mail-pl1-x62e.google.com (mail-pl1-x62e.google.com [2607:f8b0:4864:20::62e]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 8a7c2c1b-0ae4-11f0-9ea3-5ba50f476ded; Thu, 27 Mar 2025 09:21:55 +0100 (CET) Received: by mail-pl1-x62e.google.com with SMTP id d9443c01a7336-223f4c06e9fso12963945ad.1 for ; Thu, 27 Mar 2025 01:21:54 -0700 (PDT) Received: from localhost ([84.78.159.3]) by smtp.gmail.com with UTF8SMTPSA id d2e1a72fcca58-7390611c945sm13613107b3a.88.2025.03.27.01.21.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Mar 2025 01:21:52 -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" X-Inumbo-ID: 8a7c2c1b-0ae4-11f0-9ea3-5ba50f476ded DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1743063713; x=1743668513; darn=lists.xenproject.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=U5i/Mcx68PlazOgSRpwDyE0szi2aJd5Bd7xB7vmAT0A=; b=LsufoFwZ8OCjYbBOJRyOHbZTDENyE2Ypnsl809c4kQMR2lopwJ50C7wBoOJ8IWNgsy ljShKq4/OYj8F6RFV8Vdhh1y4LY5rcKCsQO9Zq+BXcOut4pKJncyv4aiYVZwE+B/2DG6 b3xK+LA4dM+LNyUjY86FioUPf5a9bKYYXEHPI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1743063713; x=1743668513; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=U5i/Mcx68PlazOgSRpwDyE0szi2aJd5Bd7xB7vmAT0A=; b=C7YpUC+RYJ6ek11gND4UYbo/KBGqxY2+WOhbbQ9gVQ7bYa7AB4yz3jXJOqwDavJQsV /xKKpQCP0u7OyUi6cwXO1ge1iVUYbbEbdR2au3bg/obNmy+oG4dDMlV5atvyKkHog7fL Iz8kCOArGVGaWMEqJQZ3bLyDtgKpHZckqAsO8SOWHlYfCaHme8JIJpLksylB/On3PG8J 7FXnF/6IHdQqBum++2fWOUggnF/zdOfAkh06A21El74S+AgO3s6KYJoA50sw+TIq1RIW N+HSy+y85dKERkL/BUByrMkK7l6EnKN8xJqr8PdyP9dxrYNJ9Ij/lc/0n+fg+TyHbHIa MaRw== X-Gm-Message-State: AOJu0YyzsVuY8TTe5C9OPAdp9QiNGpFAGuNjZA7dAqTKadyU/8QZ5TSa nliOU2DpMUAINv4fRRvlTZ4d+RiowjicyaCpvO2AiBIUig1cQar++T5cPuzf/gg= X-Gm-Gg: ASbGncssfT2p5rE9VikhgU8VHOwpiLIxgDhAh9yRXV7UdNm72mWgt2h2ONjMGIRbfmb wLsvhrPuPvfSslmx/SBauyLZUHJEzNdrdrY59oVUzRRdLAKt6VC5sHv4aLu42ZKJABJ7C3a6nWq rTxGrkHDfW13BMiLUNRd6riSTN72ePwY70IV0Nzt6oUgk4EZindwTqgaEUvGt0chT/wDK4hFdX1 LCofG3CeX1HRRwoIhptrh3Pf8PC8srmpiQNI5SHvyx3LWXvottJN6e4Gt2Uw4HTwMIwPGjc7WCD wP0M759Gwq6BnRyHun2M0qnjY/APn3a8J90JixLjhjwAsNlWOc0w6yB/ZndG X-Google-Smtp-Source: AGHT+IHdQ7h9Ziykt2O4Hs/wLs18dQLAj9GORRbFMeE7UsE8ytaO3FPx0XGFSKb1CpMe2HbXF4lipQ== X-Received: by 2002:a17:903:2452:b0:223:fbbe:599c with SMTP id d9443c01a7336-227efb66734mr100300845ad.19.1743063713213; Thu, 27 Mar 2025 01:21:53 -0700 (PDT) Date: Thu, 27 Mar 2025 09:21:47 +0100 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich Cc: "xen-devel@lists.xenproject.org" , Andrew Cooper Subject: Re: [PATCH] x86/CPU: don't hard-code MTRR availability Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Mar 25, 2025 at 08:18:11AM +0100, Jan Beulich wrote: > In particular if we're running virtualized, the underlying hypervisor > (which may be another Xen) may not surface MTRRs, and offer PAT only. At least for Xen, I think we offer MTRR uniformly, even on PVH guests? > Fixes: 5a281883cdc3 ("Hardcode many cpu features for x86/64 -- we know 64-bit") > Signed-off-by: Jan Beulich Acked-by: Roger Pau Monné My main concern is whether the !mtrr path is still functional. Have you tried booting the resulting hypervisor with MTRR masked on CPUID? (or alternatively short-circuiting cpu_has_mtrr == 0?) Thanks, Roger.