On Tue, Mar 23, 2021 at 12:47:24PM +0100, Daniel Vetter wrote:
+static inline bool is_cow_mapping(vm_flags_t flags)
Bit a bikeshed, but I wonder whether the public interface shouldn't be vma_is_cow_mapping. Or whether this shouldn't be rejected somewhere else, since at least in drivers/gpu we have tons of cases that don't check for this and get it all kinds of wrong I think.
remap_pfn_range handles this for many cases, but by far not for all.
Anyway patch itself lgtm:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
I would like it if io_remap_pfn_range() did not allow shared mappings at all.
IIRC it doesn't work anyway, the kernel can't reliably copy from IO pages eg the "_copy_from_user_inatomic()" under cow_user_page() will not work on s390 that requires all IO memory be accessed with special instructions.
Unfortunately I have no idea what the long ago special case of allowing COW'd IO mappings is. :\
Jason