On Thu, Mar 03, 2022 at 02:49:29PM -0800, Stefano Stabellini wrote: > On Thu, 3 Mar 2022, Christoph Hellwig wrote: > > On Wed, Mar 02, 2022 at 05:25:10PM -0800, Stefano Stabellini wrote: > > > Thinking more about it we actually need to drop the xen_initial_domain() > > > check otherwise some cases won't be functional (Dom0 not 1:1 mapped, or > > > DomU 1:1 mapped). > > > > Hmm, but that would be the case even before this series, right? > > Before this series we only have the xen_swiotlb_detect() check in > xen_mm_init, we don't have a second xen_initial_domain() check. > > The issue is that this series is adding one more xen_initial_domain() > check in xen_mm_init. In current mainline xen_mm_init calls xen_swiotlb_init unconditionally. But xen_swiotlb_init then calls xen_swiotlb_fixup after allocating the memory, which in turn calls xen_create_contiguous_region. xen_create_contiguous_region fails with -EINVAL for the !xen_initial_domain() and thus caues xen_swiotlb_fixup and xen_swiotlb_init to unwind and return -EINVAL. So as far as I can tell there is no change in behavior, but maybe I'm missing something subtle?
