On Tue, 29 Mar 2022 at 12:17, Arunpravin Paneer Selvam <arunpravin.paneerselvam@xxxxxxx> wrote: > > > > On 23/03/22 1:15 pm, Christian König wrote: > > Am 23.03.22 um 08:34 schrieb Arunpravin Paneer Selvam: > >> Add a simple check to reject any size not aligned to the > >> min_page_size. > >> > >> handle instances when size is not aligned with the min_page_size. > >> Unigine Heaven has allocation requests for example required pages > >> are 257 and alignment request is 256. To allocate the left over 1 > >> page, continues the iteration to find the order value which is 0 > >> and when it compares with min_order = 8, triggers the BUG_ON(order > >> < min_order). To avoid this problem, we added a simple check to > >> return -EINVAL if size is not aligned to the min_page_size. > >> > >> v2: Added more details to the commit description > >> > >> Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@xxxxxxx> > >> Suggested-by: Matthew Auld <matthew.auld@xxxxxxxxx> > >> --- > >> drivers/gpu/drm/drm_buddy.c | 3 +++ > >> 1 file changed, 3 insertions(+) > >> > >> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c > >> index 72f52f293249..b503c88786b0 100644 > >> --- a/drivers/gpu/drm/drm_buddy.c > >> +++ b/drivers/gpu/drm/drm_buddy.c > >> @@ -661,6 +661,9 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm, > >> if (range_overflows(start, size, mm->size)) > >> return -EINVAL; > >> > >> + if (WARN_ON(!IS_ALIGNED(size, min_page_size))) > >> + return -EINVAL; > >> + > > > > I'm not that happy with the handling here. > > > > See a minimum page size larger than the requested size is perfectly > > valid, it just means that the remaining pages needs to be trimmed. > > > > In other words when the request is to allocate 1 page with an alignment > > of 256 we just need to give the remaining 255 pages back to the allocator. > > In one of the previous mail Matthew explained that i915 expects to > return -EINVAL error code if size is not aligned to min_page_size. We could also move the WARN_ON() into i915 as a separate patch, and just change the default buddy behaviour to transparently handle the rounding + trim, if you prefer. I don't have a strong opinion. > > can we just modify in amdgpu code where we round_up the size to the > min_page_size value and keep this error handling in drm_buddy.c? > > > > Regards, > > Christian. > > > >> /* Actual range allocation */ > >> if (start + size == end) > >> return __drm_buddy_alloc_range(mm, start, size, blocks); > >> > >> base-commit: 056d47eaf6ea753fa2e21da31f9cbd8b721bbb7b > >
