On Fri, Jun 10, 2022 at 04:35:13PM -0600, Alex Williamson wrote:
> The commit referenced below subtly and inadvertently changed the logic
> to disallow pinning of zero pfns. This breaks device assignment with
> vfio and potentially various other users of gup. Exclude the zero page
> test from the negation.
>
> Fixes: 1c563432588d ("mm: fix is_pinnable_page against a cma page")
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> ---
>
> At least I assume this was inadvertent... If there's a better fix,
> please run with it as I'm out of the office the 1st half of next
> week and would like to see this fixed ASAP. Thanks!
>
> include/linux/mm.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index bc8f326be0ce..781fae17177d 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1600,7 +1600,7 @@ static inline bool is_pinnable_page(struct page *page)
> if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE)
> return false;
> #endif
> - return !(is_zone_movable_page(page) || is_zero_pfn(page_to_pfn(page)));
> + return !is_zone_movable_page(page) || is_zero_pfn(page_to_pfn(page));
Thanks for catching!
I don't think zero pfn could stay in the movable zone or CMA area.
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
