From mboxrd@z Thu Jan 1 00:00:00 1970 From: Elena Ufimtseva Subject: Re: [PATCH RFC] p2m: p2m_mmio_direct set RW permissions Date: Thu, 22 Jan 2015 07:11:09 -0800 (PST) Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: JBeulich@suse.com Cc: kevin.tian@intel.com, 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 ----- JBeulich@suse.com wrote: > >>> On 21.01.15 at 21:55, wrote: > > p2m_mmio_direct should result in setting IOMMUF_readable and > IOMMUF_writable > > flags. > > When pvh domain maps mmio regions, the EPT entries are not getting > mapped. > > This leads to IOMMU Page faults for some devices, as for example USB > Host > > controllers with embedded Debug devices. See > pvh-set-need_iommu-early RFC > > patch discussion fgor detail. > > Even more so that the two patches aren't even a series, that part > of the description belongs here, not in the other patch. > > > I will appreciate your comments and ideas in regards to this > change. > > > > Looking at Roger patches (xen/pvh: check permissions when adding > MMIO > > regions) > > the mmio memory type is proposed to be changed from p2m_mmio_direct > to > > p2m_access_rw. > > This type still does not have proper IOMMU flags mapping. > > A fundamental question is what business devices have to DMA their > own (or other devices') MMIO space. I could remotely see a need > for this for e.g. frame buffers, but I have difficulty understanding > this for USB devices. Please at the very least provide details on the > MMIO regions that those devices have, and which of them you > observed IOMMU faults on. > > Jan Hi Jan The IOMMU Page fault addresses are 0xd5d45 and 0xd5d46 in case of ThinkCentre machine. If you would like to see any other details I am happy to send them as well. With Dell Precision it is not known what addresses do trigger page faults because it just hangs. I don't have an answer why the devices need to access DMA of their MMIOs. Will ask linux usb folks. Elena