From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: Using debug-key 'o: Dump IOMMU p2m table, locks up machine Date: Sun, 02 Sep 2012 15:58:58 +0100 Message-ID: References: <40501859.20120902104331@eikelenboom.it> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <40501859.20120902104331@eikelenboom.it> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Sander Eikelenboom Cc: "wei.wang2@amd.com" , Santosh Jodh , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 02/09/2012 09:43, "Sander Eikelenboom" wrote: >> Quite simply, there likely needs to be more tracing on the IOMMU fault path. >> That's a separate concern from your keyhandler of course, but just saying >> I'd be looking for the former rather than the latter, for diagnosing >> Sander's bug. > > Are there any printk's I could add to get more relevant info about the AMD-Vi: > IO_PAGE_FAULT ? No really straightforward one. I think we need a per-IOMMU-type handler to walk the IOMMU page table for a given virtual address, and dump every page-table-entry on the path. Like an IOMMU version of show_page_walk(). Personally I would suspect this is more useful than the dump-everything handlers: just give a *full* *detailed* walk for the actually interesting virtual address (the one faulted on). > I have attached new output from xl dmesg, this time with iommu=debug on (the > option changed from 4.1 to 4.2). Not easy to glean any more from that, without extra tracing such as described above, and/or digging into the guest to find what driver-side actions are causing the faults. -- Keir > > >> -- Keir >