From xen-devel-bounces@lists.xen.org Mon Jun 02 15:34:59 2014 Received: (at maildrop) by bugs.xenproject.org; 2 Jun 2014 14:34:59 +0000 Received: from lists.xen.org ([50.57.142.19]) by bugs.xenproject.org with esmtp (Exim 4.80) (envelope-from ) id 1WrTKF-0007UQ-3H for xen-devel-maildrop-Eithu9ie@bugs.xenproject.org; Mon, 02 Jun 2014 15:34:59 +0100 Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1WrTCv-0006Fm-5l; Mon, 02 Jun 2014 14:27:25 +0000 Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1WrTCu-0006Fd-CT for xen-devel@lists.xen.org; Mon, 02 Jun 2014 14:27:24 +0000 Received: from [193.109.254.147:9067] by server-13.bemta-14.messagelabs.com id 2A/C6-23211-BC98C835; Mon, 02 Jun 2014 14:27:23 +0000 X-Env-Sender: JBeulich@suse.com X-Msg-Ref: server-6.tower-27.messagelabs.com!1401719242!8558057!1 X-Originating-IP: [130.57.118.101] X-SpamReason: No, hits=0.5 required=7.0 tests=BODY_RANDOM_LONG X-StarScan-Received: X-StarScan-Version: 6.11.3; banners=-,-,- X-VirusChecked: Checked Received: (qmail 3201 invoked from network); 2 Jun 2014 14:27:23 -0000 Received: from mail.emea.novell.com (HELO mail.emea.novell.com) (130.57.118.101) by server-6.tower-27.messagelabs.com with DHE-RSA-AES256-SHA encrypted SMTP; 2 Jun 2014 14:27:23 -0000 Received: from EMEA1-MTA by mail.emea.novell.com with Novell_GroupWise; Mon, 02 Jun 2014 15:27:22 +0100 Message-Id: <538CA5E80200007800016E34@mail.emea.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.0.0 Date: Mon, 02 Jun 2014 15:27:20 +0100 From: "Jan Beulich" To: "George Dunlap" References: <20140210080314.GA758@deinos.phlegethon.org> <20140211090202.GC92054@deinos.phlegethon.org> <20140211115553.GB97288@deinos.phlegethon.org> <52FA2C63020000780011B201@nat28.tlf.novell.com> <52FA480D.9040707@eu.citrix.com> <52FCE8BE.8050105@eu.citrix.com> <52FCF90F020000780011C29A@nat28.tlf.novell.com> <20140213162022.GE82703@deinos.phlegethon.org> <537B1E520200007800013EB7@mail.emea.novell.com> <537B4EA70200007800014085@mail.emea.novell.com> <537C769B02000078000145C2@mail.emea.novell.com> <537F09EC020000780001530D@mail.emea.novell.com> <53831FD902000078000159F9@mail.emea.novell.com> <538C3BE40200007800016AE1@mail.emea.novell.com> In-Reply-To: Mime-Version: 1.0 Content-Disposition: inline Cc: "andrew.cooper3@citrix.com" , Tim Deegan , "xen-devel@lists.xen.org" , "KeirFraser\(keir.xen@gmail.com\)" , Jun Nakajima , Yang Z Zhang , Xiantao Zhang 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 >>> On 02.06.14 at 16:06, wrote: > On Mon, Jun 2, 2014 at 7:55 AM, Jan Beulich wrote: >>>>> On 31.05.14 at 03:26, wrote: >>> On Mon, May 26, 2014 at 2:04 AM, Jan Beulich wrote: >>>>>>> On 26.05.14 at 10:16, wrote: >>>>> Jan Beulich wrote on 2014-05-23: >>>>>> Btw., I think I just spotted a second thing not working without split page >>>>> tables: >>>>>> mem-access (which doesn't and imo shouldn't depend on !need_iommu(), >>>>>> other than mem-sharing and mem-paging) likewise has the potential of >>>>>> creating entries resulting in IOMMU faults. >>>>>> >>>>> >>>>> I don't know what mem-access is? Do you mean Xenaccess? If not, can you >>>>> elaborate it or provide a link to help me to understand how it works? >>>> >>>> The (example) tool indeed is named xen-access. See XENMEM_access_op >>>> (used to be HVMOP_{get,set}_mem_access). >>>> >>> >>> The tool xen-access is located in tools/tests, and I think that this >>> is used mostly by developers who know what they are doing. >> >> The tool is, indeed. But the underlying feature clearly isn't limited >> to or solely intended for developers. >> >>> If we had separate VT-d page tables, they might observe confusing >>> results; even if they write-protect pages, somebody (i.e. I/O devices) >>> modifies those pages. >>> To me, observing IOMMU faults seems consistent with the consequence of >>> changes to guest memory permission. >> >> And I would agree if these faults were restartable. You're certainly >> aware that a not too large amount of faults within a reasonably short >> period of time will lead to the device being turned off, with quite likely >> fatal consequences to the guest. > > Sure -- but there are a number of features (PoD, paging, page sharing, > even migration) which are incompatible with pass-through, and the user > is simply not allowed to use them together. Why not just add this one > to the list? Considering that mem-access came at about the same time or even later than mem-paging and mem-sharing, I was silently assuming that it wasn't enforcing the same restrictions as the other two for a reason. Maybe it was just forgotten... Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel