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 X-Spam-Level: X-Spam-Status: No, score=-10.9 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F1A0C433E1 for ; Tue, 18 Aug 2020 14:53:31 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 521A72080C for ; Tue, 18 Aug 2020 14:53:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=citrix.com header.i=@citrix.com header.b="c8vSyh6e" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 521A72080C Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=citrix.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k82zJ-00076o-8F; Tue, 18 Aug 2020 14:53:21 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1k82zI-00076j-MU for xen-devel@lists.xenproject.org; Tue, 18 Aug 2020 14:53:20 +0000 X-Inumbo-ID: 2d1363cd-4452-4593-ad78-407fe64fa620 Received: from esa6.hc3370-68.iphmx.com (unknown [216.71.155.175]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 2d1363cd-4452-4593-ad78-407fe64fa620; Tue, 18 Aug 2020 14:53:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=citrix.com; s=securemail; t=1597762399; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=VMNtGKCmpYPA1KUfgd8F2vWiAZaSb6+mA6M1usuJWUY=; b=c8vSyh6eN8EGTTBN6IdIm0G7azoV0W7dn9Uu0XpfIP10xry8ntuqFGvO 252FWTi2/aK15YCFH93ditXObwKebLDxmcYfdAh7yn6pvYQFcPVhat0I4 K1IM2dHwOiyK9Y7nYoXuQvCM27UUQKfI/Y2GfnHoMlfkWPAZMVFlJ/uBU 8=; Authentication-Results: esa6.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none IronPort-SDR: XDTIIoBsFcvPkrxcBVl+PGfnL2jZXQltep7NbcsPA+Rfx0ajBJC2iQdFrPzkekwBTFisxMLzRN Y/Niv0IxGA8YXaL+zf3RHy8LJFivIiCxVZJSj2izF88OMCrzxFnkk6P8OcTzq82dip6CbDROHU rZjlmEb6hB3NVZCpDarCacKjiYU/IdjPMVr5mt0OMIEUJp1Ya+XjDeCv0eNlWphLhBuq2Urvt5 0tdQYFx3tRPz8F7DvOwDv2x5YeeKmNN3oMT3UN0eTJl57OvfNOl/VvHtQmZtI14MRM38V/6pUo TM4= X-SBRS: 2.7 X-MesageID: 25092713 X-Ironport-Server: esa6.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.76,327,1592884800"; d="scan'208";a="25092713" Subject: Re: [PATCH 2/8] x86/svm: silently drop writes to SYSCFG and related MSRs To: Roger Pau Monne , CC: Jan Beulich , Wei Liu References: <20200817155757.3372-1-roger.pau@citrix.com> <20200817155757.3372-3-roger.pau@citrix.com> From: Andrew Cooper Message-ID: <667ecceb-e111-5da5-74f9-9b1cc8628a6a@citrix.com> Date: Tue, 18 Aug 2020 15:53:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200817155757.3372-3-roger.pau@citrix.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Content-Language: en-GB X-ClientProxiedBy: AMSPEX02CAS02.citrite.net (10.69.22.113) To AMSPEX02CL02.citrite.net (10.69.22.126) X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 17/08/2020 16:57, Roger Pau Monne wrote: > diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c > index ca3bbfcbb3..671cdcb724 100644 > --- a/xen/arch/x86/hvm/svm/svm.c > +++ b/xen/arch/x86/hvm/svm/svm.c > @@ -1917,6 +1917,13 @@ static int svm_msr_read_intercept(unsigned int msr, uint64_t *msr_content) > goto gpf; > break; > > + case MSR_K8_TOP_MEM1: > + case MSR_K8_TOP_MEM2: > + case MSR_K8_SYSCFG: > + /* Return all 0s. */ > + *msr_content = 0; On a Rome box, these are the normal values: 0xc0010010 (SYSCFG) 0x740000 0xc001001a (MEM1) 0xb0000000 0xc001001d (MEM2) 0x3c50000000 The SYSCFG bits are MtrrFixDramEn[18], MtrrVarDramEn[20], MtrrTom2En[21] and Tom2ForceMemTypeWB[22].  In particular, bits 18 and 20 are expected to be set by the system firmware. Clearly we shouldn't be leaking TOP_MEM{1,2} into guests, but Xen also doesn't have enough information to set these correctly yet either. At a minimum, I think SYSCFG wants to report 0x40000 which means "the fixed MTRRs behave as expected", and the other bits being clear should mean that TOP_MEM{1,2} aren't enabled. ~Andrew