On Fri, Oct 23, 2020 at 09:48:58AM +0200, Jean-Philippe Brucker wrote: > Arm CPUs and SMMU support 4k, 16k and 64k page sizes. I don't think 16k is > used anywhere but some distributions chose 64k (RHEL, I think?), others > 4k, so we need to support both. > > Unfortunately as noted above host64k-guest4k is not possible without > adding a negotiation mechanism to virtio-iommu, host VFIO and IOMMU > driver.
I see. Then it seems we would still need to support host4k-guest64k. Maybe for assigned case, we can simply AND all the psize_masks of all the vfio containers that supported to replace the default psize mask (TARGET_PAGE_SIZE) without caring about whether it's shrinking or not? Note that current patch only update config.psize_mask to the new one, but I think we need to calculate the subset of all containers rather than a simply update. Then with the help of 39b3b3c9cac1 imho we'll gracefully fail the probe if the psize is not suitable anyway, e.g., host64k-guest4k. Thanks, -- Peter Xu
