Hi Jean, > From: Jean-Philippe Brucker [mailto:jean-philippe.brucker@xxxxxxx] > Sent: Thursday, September 27, 2018 9:38 PM > To: Liu, Yi L <yi.l.liu@xxxxxxxxx>; Joerg Roedel <joro@xxxxxxxxxx> > Subject: Re: [PATCH v3 03/10] iommu/sva: Manage process address spaces > > On 27/09/2018 04:22, Liu, Yi L wrote: > >> For the "classic" vfio-pci case, "SVA in guest" still means giving the > >> guest control over the whole PASID table. > > > > No, if giving guest control over the whole PASID table, it means guest may have > > its own PASID namespace. right? And for vfio-mdev case, it gets PASID from host. > > So there would be multiple PASID namespaces. Thinking about the following > scenario: > > > > A PF/VF assigned to a VM via "classic" vfio-pci. And an assignable-device-interface > > assigned to this VM via vfio-mdev. If an application in this VM tries to manipulate > > these two "devices", it should have the same PASID programmed to them. right? > > But as the above comments mentioned, for vfio-pci case, it would get a PASID > from > > its own PASID namespace. While the vfio-mdev case would get a PASID from host. > > This would result in conflict. > > Ah I see, if the host assigns an ADI via vfio-mdev and a PCI function > via vfio-pci to the same VM, the guest needs to use the paravirtualized > PASID allocator for the PCI device as well, not just the ADI. In fact > all guest PASIDs need to be allocated through one PV channel, even if > the VM has other vIOMMUs that don't support PV. But I suppose that kind > of VM is unrealistic. yes, such kind of VM is unrealistic. :) > However for SMMUv3 we'll still use the > bind_pasid_table for vfio-pci and let the guest allocate PASIDs, since > the PASID table lives in guest-physical space. I think it's ok. This doesn’t result in any conflict. > > In any case, for the patch series at hand, it means that iommu-sva will > need assistance from the vt-d driver to allocate PASIDs: host uses the > generic allocator, guest uses the PV one. Exactly. > I guess the mm_alloc() op could do that? Do you mean the io_mm_alloc in your SVA patch series? We've got some patch for the PV one. Allen (Baolu Lu) is preparing to send it out for review. I guess we can have more alignment during that patch reviewing. Thanks, Yi Liu
