On Tue, Jul 21, 2026 at 12:12:01PM -0700, Matthew Brost wrote:
> On Tue, Jul 21, 2026 at 12:40:38PM +0200, Jan Stancek wrote:
> > HPAGE_PMD_SHIFT expands to BUILD_BUG() when CONFIG_PGTABLE_HAS_HUGE_LEAVES
> > is not set, causing a compile error when both CONFIG_TRANSPARENT_HUGEPAGE
> > and CONFIG_HUGETLB_PAGE are disabled:
> >
> > drivers/gpu/drm/drm_pagemap.c:480:12: error: call to
> > '__compiletime_assert_458'
> > declared with 'error' attribute: BUILD_BUG failed
> > 480 | order = HPAGE_PMD_ORDER;
> > | ^
> > include/linux/huge_mm.h:117:26: note: expanded from macro 'HPAGE_PMD_ORDER'
> > 117 | #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
> > | ^
> > include/linux/huge_mm.h:113:28: note: expanded from macro 'HPAGE_PMD_SHIFT'
> > 113 | #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
> >
> > Guard the two HPAGE_PMD_ORDER uses with CONFIG_ARCH_ENABLE_THP_MIGRATION,
> > matching the pattern used in migrate_device.c.
> >
> > Fixes: 139ab31aea8a ("drm/pagemap: Correct cpages calculation for
> > migrate_vma_setup")
> > Reported-by: kernel test robot <[email protected]>
> > Closes: https://lore.kernel.org/r/[email protected]/
> > Signed-off-by: Jan Stancek <[email protected]>
> > ---
> > drivers/gpu/drm/drm_pagemap.c | 10 ++++++++--
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
> > index 15c78eca180b..53a78752c8be 100644
> > --- a/drivers/gpu/drm/drm_pagemap.c
> > +++ b/drivers/gpu/drm/drm_pagemap.c
> > @@ -578,10 +578,13 @@ static int drm_pagemap_cpages(unsigned long
> > *migrate_pfn, unsigned long npages)
> > folio = page_folio(page);
> > order = folio_order(folio);
> > cpages += NR_PAGES(order);
> > - } else if (migrate_pfn[i] & MIGRATE_PFN_COMPOUND) {
> > + }
> > +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
> > + else if (migrate_pfn[i] & MIGRATE_PFN_COMPOUND) {
> > order = HPAGE_PMD_ORDER;
>
> Would it be do something like this at the top of the file...
>
> #ifdef HPAGE_PMD_ORDER
> #define DRM_PAGEMAP_PMD_ORDER HPAGE_PMD_ORDER
> #else
> #define DRM_PAGEMAP_PMD_ORDER (-1)
> #endif
>
Opps screwed my snippet up - HPAGE_PMD_ORDER seems to be always defined...
So actually...
#if IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION)
#define DRM_PAGEMAP_PMD_ORDER HPAGE_PMD_ORDER
#else
define DRM_PAGEMAP_PMD_ORDER (-1)
#endif
Matt
> Then in common code s/HPAGE_PMD_ORDER/DRM_PAGEMAP_PMD_ORDER/
>
> I think this works as we can never get to the MIGRATE_PFN_COMPOUND code
> paths without CONFIG_ARCH_ENABLE_THP_MIGRATION enabled (see
> mm/migrate_device.c).
>
> Also btw fixing the unrelated bug Sashiko flagged in this patch.
>
> Matt
>
> > cpages += NR_PAGES(order);
> > }
> > +#endif
> >
> > i += NR_PAGES(order);
> > }
> > @@ -733,7 +736,6 @@ int drm_pagemap_migrate_to_devmem(struct
> > drm_pagemap_devmem *devmem_allocation,
> > own_pages = 0;
> >
> > for (i = 0; i < npages;) {
> > - unsigned long j;
> > struct page *page = pfn_to_page(migrate.dst[i]);
> > struct page *src_page = migrate_pfn_to_page(migrate.src[i]);
> > unsigned int order = 0;
> > @@ -763,7 +765,10 @@ int drm_pagemap_migrate_to_devmem(struct
> > drm_pagemap_devmem *devmem_allocation,
> > }
> > migrate.dst[i] = migrate_pfn(migrate.dst[i]);
> >
> > +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
> > if (migrate.src[i] & MIGRATE_PFN_COMPOUND) {
> > + unsigned long j;
> > +
> > drm_WARN_ONCE(dpagemap->drm, src_page &&
> > folio_order(page_folio(src_page)) !=
> > HPAGE_PMD_ORDER,
> > "Unexpected folio order\n");
> > @@ -774,6 +779,7 @@ int drm_pagemap_migrate_to_devmem(struct
> > drm_pagemap_devmem *devmem_allocation,
> > for (j = 1; j < NR_PAGES(order) && i + j < npages; j++)
> > migrate.dst[i + j] = 0;
> > }
> > +#endif
> >
> > drm_pagemap_get_devmem_page(page, order, zdd);
> >
> > --
> > 2.52.0
> >
