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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6DB41C433DF for ; Fri, 22 May 2020 10:28:13 +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 3D1BD20757 for ; Fri, 22 May 2020 10:28:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D1BD20757 Authentication-Results: mail.kernel.org; dmarc=fail (p=none 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 1jc4u6-0003fg-OB; Fri, 22 May 2020 10:27:50 +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 1jc4u5-0003fb-IE for xen-devel@lists.xenproject.org; Fri, 22 May 2020 10:27:49 +0000 X-Inumbo-ID: e1fee3ce-9c16-11ea-abaf-12813bfff9fa Received: from esa2.hc3370-68.iphmx.com (unknown [216.71.145.153]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id e1fee3ce-9c16-11ea-abaf-12813bfff9fa; Fri, 22 May 2020 10:27:48 +0000 (UTC) Authentication-Results: esa2.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none IronPort-SDR: 2Wg7ssBM/W1QFfjkaBmKGEA0nhL9lqdJdx1//WCDmf09/2x8MkjW+CVgw7o5NSkFBsQ7/087LY KqrJOHwi66w8+q0s7I/cjr90EvW6JQ8V9M2i+k6P2LkoEeoA+fQD3HpNtOr9FuYSSr46RUkwuk /XLJdT/1gUJJrnliK2B2zOe1dJPTUQhqKFb/A58osTid8vvWxqJzR53J51MivFDqCr1cVqTRWU ylD/i3ObDp7jYj7gKhmKzdfV3RWIGXi4Jp8ahRiUtS+gJY00wPld6XZrXXWzOPw/RMywwBkCyn W/Y= X-SBRS: 2.7 X-MesageID: 18195004 X-Ironport-Server: esa2.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.73,421,1583211600"; d="scan'208";a="18195004" Subject: Re: [PATCH] x86/svm: retry after unhandled NPT fault if gfn was marked for recalculation To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: <1590097438-28829-1-git-send-email-igor.druzhinin@citrix.com> <20200522100846.GV54375@Air-de-Roger> <04ec4ab4-a121-c5be-0a65-316e237dd793@citrix.com> <20200522102339.GX54375@Air-de-Roger> From: Igor Druzhinin Message-ID: Date: Fri, 22 May 2020 11:27:38 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200522102339.GX54375@Air-de-Roger> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit 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: , Cc: xen-devel@lists.xenproject.org, wl@xen.org, jbeulich@suse.com, andrew.cooper3@citrix.com Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 22/05/2020 11:23, Roger Pau Monné wrote: > On Fri, May 22, 2020 at 11:14:24AM +0100, Igor Druzhinin wrote: >> On 22/05/2020 11:08, Roger Pau Monné wrote: >>> On Thu, May 21, 2020 at 10:43:58PM +0100, Igor Druzhinin wrote: >>>> If a recalculation NPT fault hasn't been handled explicitly in >>>> hvm_hap_nested_page_fault() then it's potentially safe to retry - >>>> US bit has been re-instated in PTE and any real fault would be correctly >>>> re-raised next time. >>>> >>>> This covers a specific case of migration with vGPU assigned on AMD: >>>> global log-dirty is enabled and causes immediate recalculation NPT >>>> fault in MMIO area upon access. This type of fault isn't described >>>> explicitly in hvm_hap_nested_page_fault (this isn't called on >>>> EPT misconfig exit on Intel) which results in domain crash. >>> >>> Couldn't direct MMIO regions be handled like other types of memory for >>> the purposes of logdiry mode? >>> >>> I assume there's already a path here used for other memory types when >>> logdirty is turned on, and hence would seem better to just make direct >>> MMIO regions also use that path? >> >> The proble of handling only MMIO case is that the issue still stays. >> It will be hit with some other memory type since it's not MMIO specific. >> The issue is that if global recalculation is called, the next hit to >> this type will cause a transient fault which will not be handled >> correctly after a due fixup by neither of our handlers. > > I admit I should go look at the code, but for example RAM p2m types > don't require this fix, so I assume there's some different path taken > in that case that avoids all this? > > Ie: when global logdirty is enabled you will start to get nested page > faults for every access, yet only direct MMIO types require this fix? It's not "only MMIO" - it's just MMIO area is hit in my particular case. I'd prefer this fix to address the general issue otherwise for SVM we would have to write handlers in hvm_hap_nested_page_fault() for every case as soon as we hit it. Igor