From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Wood Subject: Re: [PATCH 0/9 v2] vfio-pci: add support for Freescale IOMMU (PAMU) Date: Thu, 21 Nov 2013 14:47:15 -0600 Message-ID: <1385066835.1403.489.camel@snotra.buserror.net> References: <1384838233-24847-1-git-send-email-Bharat.Bhushan@freescale.com> <1384973243.2879.361.camel@ul30vt.home> <6A3DF150A5B70D4F9B66A25E3F7C888D0721D9AC@039-SN2MPN1-012.039d.mgd.msft.net> <1385066603.2879.414.camel@ul30vt.home> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1385066603.2879.414.camel-85EaTFmN5p//9pzu0YdTqQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Alex Williamson Cc: "linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "agraf-l3A5Bk7waGM@public.gmane.org" , Stuart Yoder , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org" , "linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: iommu@lists.linux-foundation.org On Thu, 2013-11-21 at 13:43 -0700, Alex Williamson wrote: > On Thu, 2013-11-21 at 11:20 +0000, Bharat Bhushan wrote: > > > > > -----Original Message----- > > > From: Alex Williamson [mailto:alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org] > > > Sent: Thursday, November 21, 2013 12:17 AM > > > To: Bhushan Bharat-R65777 > > > Cc: joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org; bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org; agraf-l3A5Bk7waGM@public.gmane.org; Wood Scott-B07421; > > > Yoder Stuart-B08248; iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org; linux- > > > pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org; linux- > > > kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; Bhushan Bharat-R65777 > > > Subject: Re: [PATCH 0/9 v2] vfio-pci: add support for Freescale IOMMU (PAMU) > > > > > > Is VFIO_IOMMU_PAMU_GET_MSI_BANK_COUNT per aperture (ie. each vfio user has > > > $COUNT regions at their disposal exclusively)? > > > > Number of msi-bank count is system wide and not per aperture, But will be setting windows for banks in the device aperture. > > So say if we are direct assigning 2 pci device (both have different iommu group, so 2 aperture in iommu) to VM. > > Now qemu can make only one call to know how many msi-banks are there but it must set sub-windows for all banks for both pci device in its respective aperture. > > I'm still confused. What I want to make sure of is that the banks are > independent per aperture. For instance, if we have two separate > userspace processes operating independently and they both chose to use > msi bank zero for their device, that's bank zero within each aperture > and doesn't interfere. Or another way to ask is can a malicious user > interfere with other users by using the wrong bank. Thanks, They can interfere. With this hardware, the only way to prevent that is to make sure that a bank is not shared by multiple protection contexts. For some of our users, though, I believe preventing this is less important than the performance benefit. -Scott