From xen-devel-bounces@lists.xen.org Mon Feb 10 08:08:28 2014 Received: (at maildrop) by bugs.xenproject.org; 10 Feb 2014 08:08:28 +0000 Received: from lists.xen.org ([50.57.142.19]) by bugs.xenproject.org with esmtp (Exim 4.80) (envelope-from ) id 1WClum-0003Ep-9F for xen-devel-maildrop-Eithu9ie@bugs.xenproject.org; Mon, 10 Feb 2014 08:08:28 +0000 Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1WClpp-0001c8-4N; Mon, 10 Feb 2014 08:03:21 +0000 Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1WClpn-0001bz-VO for xen-devel@lists.xen.org; Mon, 10 Feb 2014 08:03:20 +0000 Received: from [85.158.139.211:2337] by server-2.bemta-5.messagelabs.com id 90/30-23037-7C788F25; Mon, 10 Feb 2014 08:03:19 +0000 X-Env-Sender: tim@xen.org X-Msg-Ref: server-3.tower-206.messagelabs.com!1392019398!2799465!1 X-Originating-IP: [5.39.92.215] X-SpamReason: No, hits=0.2 required=7.0 tests=RCVD_ILLEGAL_IP X-StarScan-Received: X-StarScan-Version: 6.9.16; banners=-,-,- X-VirusChecked: Checked Received: (qmail 1314 invoked from network); 10 Feb 2014 08:03:18 -0000 Received: from deinos.phlegethon.org (HELO mail.phlegethon.org) (5.39.92.215) by server-3.tower-206.messagelabs.com with DHE-RSA-AES256-SHA encrypted SMTP; 10 Feb 2014 08:03:18 -0000 Received: from tjd by mail.phlegethon.org with local (Exim 4.82 (FreeBSD)) (envelope-from ) id 1WClpi-0000Jv-D2; Mon, 10 Feb 2014 08:03:14 +0000 Date: Mon, 10 Feb 2014 09:03:14 +0100 From: Tim Deegan To: Yang Zhang Message-ID: <20140210080314.GA758@deinos.phlegethon.org> References: <1392012840-22555-1-git-send-email-yang.z.zhang@intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1392012840-22555-1-git-send-email-yang.z.zhang@intel.com> User-Agent: Mutt/1.5.22 (2013-10-16) X-SA-Known-Good: Yes X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tim@xen.org X-SA-Exim-Scanned: No (on mail.phlegethon.org); SAEximRunCond expanded to false Cc: andrew.cooper3@citrix.com, xiantao.zhang@intel.com, JBeulich@suse.com, xen-devel@lists.xen.org Subject: Re: [Xen-devel] [PATCH] Don't track all memory when enabling log dirty to track vram X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org At 14:14 +0800 on 10 Feb (1392038040), Yang Zhang wrote: > From: Yang Zhang > > When enabling log dirty mode, it sets all guest's memory to readonly. > And in HAP enabled domain, it modifies all EPT entries to clear write bit > to make sure it is readonly. This will cause problem if VT-d shares page > table with EPT: the device may issue a DMA write request, then VT-d engine > tells it the target memory is readonly and result in VT-d fault. So that's a problem even if only the VGA framebuffer is being tracked -- DMA from a passthrough device will either cause a spurious error or fail to update the dirt bitmap. I think it would be better not to allow VT-d and EPT to share pagetables in cases where devices are passed through (i.e. all cases where VT-d is in use). Tim. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel