> -----Original Message----- > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > Sent: Friday, November 22, 2013 2:31 AM > To: Wood Scott-B07421 > Cc: Bhushan Bharat-R65777; linux-pci@xxxxxxxxxxxxxxx; agraf@xxxxxxx; Yoder > Stuart-B08248; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx; linuxppc- > dev@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 0/9 v2] vfio-pci: add support for Freescale IOMMU (PAMU) > > On Thu, 2013-11-21 at 14:47 -0600, Scott Wood wrote: > > 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. Want to be sure of how 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. So should we let this patch series in without protection? > > I think we need some sort of ownership model around the msi banks then. > Otherwise there's nothing preventing another userspace from attempting an MSI > based attack on other users, or perhaps even on the host. VFIO can't allow > that. Thanks, We have very few (3 MSI bank on most of chips), so we can not assign one to each userspace. What we can do is host and userspace does not share a MSI bank while userspace will share a MSI bank. Thanks -Bharat > > Alex > ��.n��������+%������w��{.n�����{���"�)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
