diff options
| author | George Spelvin <lkml@SDF.ORG> | 2020-03-25 19:24:29 +0000 |
|---|---|---|
| committer | Jani Nikula <jani.nikula@intel.com> | 2020-08-19 15:23:36 +0300 |
| commit | c43a87f537d19499e51a6f013331f196d8f0ddbe (patch) | |
| tree | 96849c942010e4c7184db5229a2e8fc2f0cf2f8b /drivers/gpu/drm/i915 | |
| parent | c67f0c28311c44597ecd8e14d152d1775c367cdf (diff) | |
drm/i915/selftests: Avoid passing a random 0 into ilog2
igt_mm_config() calls ilog2() on the (pseudo)random 21-bit number
s>>12. Once in 2 million seeds, this is zero and ilog2 summons
the nasal demons.
There was an attempt to handle this case with a max(), but that's
too late; ms could already be something bizarre.
Given that the low 12 bits of s and ms are always zero, it's a lot
simpler just to divide them by 4096, then everything fits into 32
bits, and we can easily generate a random number 1 <= s <= 0x1fffff.
Fixes: 14d1b9a6247c ("drm/i915: buddy allocator")
Signed-off-by: George Spelvin <lkml@sdf.org>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200325192429.GA8865@SDF.ORG
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
(cherry picked from commit 21118e8e56479ef33460fbd63a5ad0535843b666)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Diffstat (limited to 'drivers/gpu/drm/i915')
| -rw-r--r-- | drivers/gpu/drm/i915/selftests/i915_buddy.c | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/drivers/gpu/drm/i915/selftests/i915_buddy.c b/drivers/gpu/drm/i915/selftests/i915_buddy.c index 939a6caebb03..632b912b0bc9 100644 --- a/drivers/gpu/drm/i915/selftests/i915_buddy.c +++ b/drivers/gpu/drm/i915/selftests/i915_buddy.c @@ -8,8 +8,6 @@ #include "../i915_selftest.h" #include "i915_random.h" -#define SZ_8G (1ULL << 33) - static void __igt_dump_block(struct i915_buddy_mm *mm, struct i915_buddy_block *block, bool buddy) @@ -281,18 +279,22 @@ static int igt_check_mm(struct i915_buddy_mm *mm) static void igt_mm_config(u64 *size, u64 *chunk_size) { I915_RND_STATE(prng); - u64 s, ms; + u32 s, ms; /* Nothing fancy, just try to get an interesting bit pattern */ prandom_seed_state(&prng, i915_selftest.random_seed); - s = i915_prandom_u64_state(&prng) & (SZ_8G - 1); - ms = BIT_ULL(12 + (prandom_u32_state(&prng) % ilog2(s >> 12))); - s = max(s & -ms, ms); + /* Let size be a random number of pages up to 8 GB (2M pages) */ + s = 1 + i915_prandom_u32_max_state((BIT(33 - 12)) - 1, &prng); + /* Let the chunk size be a random power of 2 less than size */ + ms = BIT(i915_prandom_u32_max_state(ilog2(s), &prng)); + /* Round size down to the chunk size */ + s &= -ms; - *chunk_size = ms; - *size = s; + /* Convert from pages to bytes */ + *chunk_size = (u64)ms << 12; + *size = (u64)s << 12; } static int igt_buddy_alloc_smoke(void *arg) |