From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: [PATCH v3] AMD/intremap: Prevent use of per-device vector maps until irq logic is fixed Date: Mon, 17 Jun 2013 09:55:59 +0100 Message-ID: <51BECF1F.7050104@eu.citrix.com> References: <51B5E1CD02000078000DCA59@nat28.tlf.novell.com> <51BBBF9D.9060404@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51BBBF9D.9060404@amd.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: Suravee Suthikulanit Cc: Keir Fraser , Andrew Cooper , Jacob Shin , xen-devel@lists.xen.org, Jan Beulich , "Hurwitz, Sherry" List-Id: xen-devel@lists.xenproject.org On 15/06/13 02:13, Suravee Suthikulanit wrote: > On 6/10/2013 7:25 AM, Jan Beulich wrote: >>>>> On 04.06.13 at 18:38, Andrew Cooper >>>>> wrote: >>> XSA-36 changed the default vector map mode from global to >>> per-device. This is >>> because a global vector map does not prevent one PCI device from >>> impersonating >>> another and launching a DoS on the system. >>> >>> However, the per-device vector map logic is broken for devices with >>> multiple >>> MSI-X vectors, which can either result in a failed ASSERT() or >>> misprogramming >>> of a guests interrupt remapping tables. The core problem is not >>> trivial to >>> fix. >>> >>> In an effort to get AMD systems back to a non-regressed state, >>> introduce a >>> new >>> type of vector map called per-device-global. This uses per-device >>> vector maps >>> in the IOMMU, but uses a single used_vector map for the core IRQ logic. >>> >>> This patch is intended to be removed as soon as the per-device logic >>> is fixed >>> correctly. >>> >>> Signed-off-by: Andrew Cooper >> Suravee, Jacob, >> >> no opinion on this at all? I've been talked into considering this >> acceptable > > Sorry for late reply, and for having missed this conversation previously. > > If we have to go with this solution temporary until we have the > permanent fix. > I think that is okay with me. Although, would you mind pointing out > the affect > of having "per-device" vs. "global" irq vector map? I am not quite > familiar > with the differences. > >> (with a small coding style fixup, and with the question on >> the usefulness of the final warning message - imo redundant with the >> immediately preceding message that is being left untouched) > > I also think the messages are quite confusing. Actually, now that we > can have > irq vector map and intremap map with different mode, we should be more > explicit > in the message. > > Also, the message "Not overriding irq_vector_map setting" is confusing > to me. > > Would you mind considering the attached patch? Here is the sample output > > (XEN) AMD-Vi: IOMMU 0 Enabled. > (XEN) AMD-Vi BUG: per-device vector map logic is broken. Using > per-device-global maps instead until a fix is found At the very least it can't say BUG -- that needs to be reserved for things that actually cause the host to crash (a la BUG_ON()). -George