On 17.02.2021 12:03, Julien Grall wrote: > On 17/02/2021 10:46, Jan Beulich wrote: >> Mappings for a domain's own pages should already be present in the >> IOMMU. While installing the same mapping again is merely redundant (and >> inefficient), removing the mapping when the grant mapping gets removed >> is outright wrong in this case: The mapping was there before the map, so >> should remain in place after unmapping. >> >> This affects >> - Arm Dom0 in the direct mapped case, >> - x86 PV Dom0 in the "iommu=dom0-strict" / "dom0-iommu=strict" cases, >> - all x86 PV DomU-s, including driver domains. >> >> Reported-by: Rahul Singh <rahul.si...@arm.com> >> Signed-off-by: Jan Beulich <jbeul...@suse.com> >> >> --- a/xen/common/grant_table.c >> +++ b/xen/common/grant_table.c >> @@ -1243,7 +1243,7 @@ map_grant_ref( >> goto undo_out; >> } >> >> - need_iommu = gnttab_need_iommu_mapping(ld); >> + need_iommu = ld != rd && gnttab_need_iommu_mapping(ld); > > AFAICT, the owner of the page may not always be rd. So do we want to > check against the owner instead?
For the DomIO case - specifically not. And the DomCOW case can't happen when an IOMMU is in use. Did I overlook any other cases where the page may not be owned by rd? Jan
