[PATCH v11 63/65] drm_buddy: fix 64-bit truncation in power-of-2 rounding

[Jim Cromie <jim.cromie@gmail.com>]

The standard roundup_pow_of_two() and rounddown_pow_of_two() macros use
unsigned long internally, which on 32-bit architectures (like arm32) is
a 32-bit type.

drm_test_buddy_alloc_exceeds_max_order() uses the on a u64 value,
where they silently truncate the 10GB allocation, giving unexpected
success in DRM-CI.  (see below the snip).

Fix this by replacing the standard macros with safe 64-bit
power-of-two calculations using ilog2().

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---

    [23:19:40] [PASSED] drm_test_buddy_alloc_clear
    [23:19:40] [PASSED] drm_test_buddy_alloc_range_bias
    [23:19:41] [PASSED] drm_test_buddy_fragmentation_performance
    [23:19:41]     # drm_test_buddy_alloc_exceeds_max_order: EXPECTATION FAILED at drivers/gpu/drm/tests/drm_buddy_test.c:889
    [23:19:41]     Expected err == -22, but
    [23:19:41]         err == 0 (0x0)
    [23:19:41] ------------[ cut here ]------------
    [23:19:41] WARNING: drivers/gpu/drm/drm_buddy.c:405 at drm_buddy_fini+0x114/0x1b8, CPU#0: kunit_try_catch/74
    [23:19:41] CPU: 0 UID: 0 PID: 74 Comm: kunit_try_catch Tainted: G                 N  7.0.0-rc1-gdfb0bcedd08a #1 VOLUNTARY
    [23:19:41] Tainted: [N]=TEST
    [23:19:41] Hardware name: Generic DT based system
    [23:19:41] Call trace:
    [23:19:41]  unwind_backtrace from show_stack+0x10/0x14
    [23:19:41]  show_stack from dump_stack_lvl+0x3c/0x4c
    [23:19:41]  dump_stack_lvl from __warn+0xe8/0x1c4
    [23:19:41]  __warn from warn_slowpath_fmt+0xa4/0xc0
    [23:19:41]  warn_slowpath_fmt from drm_buddy_fini+0x114/0x1b8
    [23:19:41]  drm_buddy_fini from drm_test_buddy_alloc_exceeds_max_order+0x1c8/0x36c
    [23:19:41]  drm_test_buddy_alloc_exceeds_max_order from kunit_try_run_case+0x78/0x1c8
    [23:19:41]  kunit_try_run_case from kunit_generic_run_threadfn_adapter+0x1c/0x34
    [23:19:41]  kunit_generic_run_threadfn_adapter from kthread+0x108/0x134
    [23:19:41]  kthread from ret_from_fork+0x14/0x28
    [23:19:41] Exception stack(0xf0bd5fb0 to 0xf0bd5ff8)
    [23:19:41] 5fa0:                                     00000000 00000000 00000000 00000000
    [23:19:41] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
    [23:19:41] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
    [23:19:41] ---[ end trace 0000000000000000 ]---
    [23:19:41]     # drm_test_buddy_alloc_exceeds_max_order: drivers/gpu/drm/drm_buddy.c:406: buddy_fini() root
    [23:19:41] ------------[ cut here ]------------
    [23:19:41] WARNING: drivers/gpu/drm/drm_buddy.c:414 at drm_buddy_fini+0x1b4/0x1b8, CPU#0: kunit_try_catch/74
    [23:19:41] CPU: 0 UID: 0 PID: 74 Comm: kunit_try_catch Tainted: G        W        N  7.0.0-rc1-gdfb0bcedd08a #1 VOLUNTARY
    [23:19:41] Tainted: [W]=WARN, [N]=TEST
    [23:19:41] Hardware name: Generic DT based system
    [23:19:41] Call trace:
    [23:19:41]  unwind_backtrace from show_stack+0x10/0x14
    [23:19:41]  show_stack from dump_stack_lvl+0x3c/0x4c
    [23:19:41]  dump_stack_lvl from __warn+0xe8/0x1c4
    [23:19:41]  __warn from warn_slowpath_fmt+0xa4/0xc0
    [23:19:41]  warn_slowpath_fmt from drm_buddy_fini+0x1b4/0x1b8
    [23:19:41]  drm_buddy_fini from drm_test_buddy_alloc_exceeds_max_order+0x1c8/0x36c
    [23:19:41]  drm_test_buddy_alloc_exceeds_max_order from kunit_try_run_case+0x78/0x1c8
    [23:19:41]  kunit_try_run_case from kunit_generic_run_threadfn_adapter+0x1c/0x34
    [23:19:41]  kunit_generic_run_threadfn_adapter from kthread+0x108/0x134
    [23:19:41]  kthread from ret_from_fork+0x14/0x28
    [23:19:41] Exception stack(0xf0bd5fb0 to 0xf0bd5ff8)
    [23:19:41] 5fa0:                                     00000000 00000000 00000000 00000000
    [23:19:41] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
    [23:19:41] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
    [23:19:41] ---[ end trace 0000000000000000 ]---
    [23:19:41] [FAILED] drm_test_buddy_alloc_exceeds_max_order
    [23:19:41]     # drm_buddy: Testing DRM buddy manager, with random_seed=0xacce106c
    [23:19:41]     # module: drm_buddy_test
    [23:19:41] # drm_buddy: pass:8 fail:1 skip:0 total:9
---
 drivers/gpu/buddy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/buddy.c b/drivers/gpu/buddy.c
index 52686672e99f..ed4d33a30687 100644
--- a/drivers/gpu/buddy.c
+++ b/drivers/gpu/buddy.c
@@ -1091,7 +1091,7 @@ static int __alloc_contig_try_harder(struct gpu_buddy *mm,
 	u64 modify_size;
 	int err;
 
-	modify_size = rounddown_pow_of_two(size);
+	modify_size = 1ULL << ilog2(size);
 	pages = modify_size >> ilog2(mm->chunk_size);
 	order = fls(pages) - 1;
 	if (order == 0)
@@ -1318,7 +1318,7 @@ int gpu_buddy_alloc_blocks(struct gpu_buddy *mm,
 
 	/* Roundup the size to power of 2 */
 	if (flags & GPU_BUDDY_CONTIGUOUS_ALLOCATION) {
-		size = roundup_pow_of_two(size);
+		size = 1ULL << (ilog2(size - 1) + 1);
 		min_block_size = size;
 		/*
 		 * Normalize the requested size to min_block_size for regular allocations.
-- 
2.53.0