On Tue, Aug 24, 2021 at 10:48:17PM -0500, Alex Sierra wrote: > In this case, this is used to migrate pages from device memory, back to > system memory. This particular device memory type should be accessible > by the CPU, through IOMEM access. Typically, zone device public type > memory falls into this category. > > Signed-off-by: Alex Sierra <alex.sierra@xxxxxxx> > --- > include/linux/migrate.h | 1 + > mm/migrate.c | 3 ++- > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > index 4bb4e519e3f5..6b16f417384f 100644 > --- a/include/linux/migrate.h > +++ b/include/linux/migrate.h > @@ -156,6 +156,7 @@ static inline unsigned long migrate_pfn(unsigned long pfn) > enum migrate_vma_direction { > MIGRATE_VMA_SELECT_SYSTEM = 1 << 0, > MIGRATE_VMA_SELECT_DEVICE_PRIVATE = 1 << 1, > + MIGRATE_VMA_SELECT_IOMEM = 1 << 2, > }; > > struct migrate_vma { > diff --git a/mm/migrate.c b/mm/migrate.c > index e3a10e2a1bb3..d4ae2da99607 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2406,7 +2406,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > if (is_write_device_private_entry(entry)) > mpfn |= MIGRATE_PFN_WRITE; > } else { > - if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) > + if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM) && > + !(migrate->flags & MIGRATE_VMA_SELECT_IOMEM)) This makes the MIGRATE_VMA_SELECT_SYSTEM and MIGRATE_VMA_SELECT_IOMEM behave entirely identifical, that is redundant. I think we need to distinguish between the dfferent cases here. I think the right check would be pfn_valid(), which should be true for system memory, and false for iomem. Also shouldn't this be called DEVICE_PUBLIC instead of IOMEM?