On Mon, Aug 08, 2022 at 10:42:24PM -0600, Alex Williamson wrote:
> The below referenced commit makes the same error as 1c563432588d ("mm: fix
> is_pinnable_page against a cma page"), re-interpreting the logic to exclude
> pinning of the zero page, which breaks device assignment with vfio.
Perhaps we need to admit we're not as good at boolean logic as we think
we are.
if (is_device_coherent_page(page))
return false;
if (is_zone_movable_page(page))
return false;
return is_zero_pfn(page_to_pfn(page));
(or whatever the right logic is ... I just woke up and I'm having
trouble parsing it).
> Link: https://lore.kernel.org/all/165490039431.944052.12458624139225785964.stgit@omen
> Fixes: f25cbb7a95a2 ("mm: add zone device coherent type memory support")
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> ---
> include/linux/mm.h | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 18e01474cf6b..772279ed7010 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1544,9 +1544,8 @@ static inline bool is_longterm_pinnable_page(struct page *page)
> if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE)
> return false;
> #endif
> - return !(is_device_coherent_page(page) ||
> - is_zone_movable_page(page) ||
> - is_zero_pfn(page_to_pfn(page)));
> + return !(is_device_coherent_page(page) || is_zone_movable_page(page)) ||
> + is_zero_pfn(page_to_pfn(page));
> }
> #else
> static inline bool is_longterm_pinnable_page(struct page *page)
>
>
>
