Re: [PATCH V3 11/13] HV/IOMMU: Enable swiotlb bounce buffer for Isolation VM

On Thu, Aug 19, 2021 at 06:11:30PM +0000, Michael Kelley wrote:

This function is manipulating page tables in the guest VM.  It is not involved
in communicating with Hyper-V, or passing PFNs to Hyper-V.  The pfn array
contains guest PFNs, not Hyper-V PFNs.  So it should use PAGE_SIZE
instead of HV_HYP_PAGE_SIZE, and similarly PAGE_SHIFT and virt_to_pfn().
If this code were ever to run on ARM64 in the future with PAGE_SIZE other
than 4 Kbytes, the use of PAGE_SIZE is correct choice.

Yes.  I just stumled over this yesterday.  I think we can actually use a
nicer helper ased around vmap_range() to simplify this exactly because it
always uses the host page size.  I hope I can draft up a RFC today.