From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH RFC 5/5] pvh: dom0 boot option to specify iommu rw ranges Date: Fri, 20 Feb 2015 15:03:04 -0500 Message-ID: <20150220200304.GH1749@l.oracle.com> References: <20150213185247.GA12753@elena.ufimtseva> <54DE7623.1000106@citrix.com> <20150213232154.GB13156@elena.ufimtseva> <54E343D4020000780006095C@mail.emea.novell.com> <54E342DA.4090600@citrix.com> <54E352BB02000078000609AE@mail.emea.novell.com> <54E34CBC.7060904@citrix.com> <20150218181537.GB11952@l.oracle.com> <54E5B7600200007800061891@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <54E5B7600200007800061891@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: Elena Ufimtseva , kevin.tian@intel.com, Andrew Cooper , tim@xen.org, xen-devel@lists.xen.org, yang.z.zhang@intel.com, boris.ostrovsky@oracle.com, roger.pau@citrix.com List-Id: xen-devel@lists.xenproject.org On Thu, Feb 19, 2015 at 09:13:52AM +0000, Jan Beulich wrote: > >>> On 18.02.15 at 19:15, wrote: > > On Tue, Feb 17, 2015 at 02:14:20PM +0000, Andrew Cooper wrote: > >> On 17/02/15 13:39, Jan Beulich wrote: > >> >>>> On 17.02.15 at 14:32, wrote: > >> >> On 17/02/15 12:36, Jan Beulich wrote: > >> >>>>>> On 14.02.15 at 00:21, wrote: > >> >>>> On Fri, Feb 13, 2015 at 10:09:39PM +0000, Andrew Cooper wrote: > >> >>>>> If I understand the problem correctly, I believe that the correct > >> >>>>> solution would be to add a dmar_rmrr[ command line parameter along the > >> >>>>> same lines as ivrs_hpet[ and ivrs_ioapic[ which allows the user to > >> >>>>> inject corrections to the ACPI tables via the command line. > >> >>>> Yes, if we agree to classify those magic locations as being not reported > >> >>>> by ACPI machinery. > >> >>> One fundamental problem for someone to use this proposed option > >> >>> in practice is - how does(s)he learn which region(s) to specify? > >> >> Trial and improvement, or find a manual for the affected system. > >> > If such an address range would appear in a manual, it would > >> > almost certainly also appear in the ACPI tables > >> > >> In an ideal world. > >> > >> > (unless by manual you mean errata documentation). > >> > >> Also a valid source of information. > > > > The way Elena found it is by looking at the EPT violations. Perhaps > > that should be also mentioned in the Documentation for said parameter? > > Along with clarifying that this is a rather fragile approach: What if > most of the time you see faults on, say, three (perhaps > consecutive) MFNs and only after many months one on a fourth? > This may be useful for developer purposes, but I very much doubt > this would be of much use for an affected production system. Well, it would help users - and us providing the arcane incantations to them - for working around strnage platforms.