Messages in this thread | | | Date | Wed, 29 Mar 2023 15:14:56 +0200 | Subject | Re: [PATCH 2/2] drm: test: Fix 32-bit issue in drm_buddy_test | From | Christian König <> |
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Am 29.03.23 um 13:28 schrieb Jani Nikula: > On Wed, 29 Mar 2023, Maíra Canal <mcanal@igalia.com> wrote: >> On 3/29/23 03:55, David Gow wrote: >>> The drm_buddy_test KUnit tests verify that returned blocks have sizes >>> which are powers of two using is_power_of_2(). However, is_power_of_2() >>> operations on a 'long', but the block size is a u64. So on systems where >>> long is 32-bit, this can sometimes fail even on correctly sized blocks. >>> >>> This only reproduces randomly, as the parameters passed to the buddy >>> allocator in this test are random. The seed 0xb2e06022 reproduced it >>> fine here. >>> >>> For now, just hardcode an is_power_of_2() implementation using >>> x & (x - 1). >>> >>> Signed-off-by: David Gow <davidgow@google.com> >> As we still didn't consolidate an implementation of is_power_of_2_u64(), > I just cooked up some patches to try to make is_power_of_2() more > flexible. I only sent them to the "CI trybot" for a quick spin first, > will post to lkml later. [1]
In the meantime I'm pushing this to drm-misc-fixes unless somebody has some last second objections.
Christian.
> > BR, > Jani. > > > [1] https://patchwork.freedesktop.org/series/115785/ > >> Reviewed-by: Maíra Canal <mcanal@igalia.com> >> >> Best Regards, >> - Maíra Canal >> >>> --- >>> >>> There are actually a couple of is_power_of_2_u64() implementations >>> already around in: >>> - drivers/gpu/drm/i915/i915_utils.h >>> - fs/btrfs/misc.h (called is_power_of_two_u64) >>> >>> So the ideal thing would be to consolidate these in one place. >>> >>> >>> --- >>> drivers/gpu/drm/tests/drm_buddy_test.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/gpu/drm/tests/drm_buddy_test.c b/drivers/gpu/drm/tests/drm_buddy_test.c >>> index f8ee714df396..09ee6f6af896 100644 >>> --- a/drivers/gpu/drm/tests/drm_buddy_test.c >>> +++ b/drivers/gpu/drm/tests/drm_buddy_test.c >>> @@ -89,7 +89,8 @@ static int check_block(struct kunit *test, struct drm_buddy *mm, >>> err = -EINVAL; >>> } >>> >>> - if (!is_power_of_2(block_size)) { >>> + /* We can't use is_power_of_2() for a u64 on 32-bit systems. */ >>> + if (block_size & (block_size - 1)) { >>> kunit_err(test, "block size not power of two\n"); >>> err = -EINVAL; >>> }
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