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@xxxxxxxxxx] > > > Sent: Thursday, November 21, 2013 12:17 AM > > > To: Bhushan Bharat-R65777 > > > Cc: joro@xxxxxxxxxx; bhelgaas@xxxxxxxxxx; agraf@xxxxxxx; Wood Scott-B07421; > > > Yoder Stuart-B08248; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux- > > > pci@xxxxxxxxxxxxxxx; linuxppc-dev@xxxxxxxxxxxxxxxx; linux- > > > kernel@xxxxxxxxxxxxxxx; 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 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
