On 4/30/2015 3:53 PM, Dave Gordon wrote:
On 30/04/15 15:33, Michel Thierry wrote:
On 4/30/2015 3:22 PM, Ville Syrjälä wrote:
On Thu, Apr 30, 2015 at 02:59:34PM +0100, Michel Thierry wrote:
The patch 69876bed7e008f5fe01538a2d47c09f2862129d0: "drm/i915/gen8:
page directories rework allocation" added an overflow warning, but the
mask had an extra 0. Use typo-prone option suggested by Dave instead.
This check will be unnecessary after gen8_alloc_va_range handles more
than 4 PDPs (48b addressing).
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Dave Gordon <david.s.gordon@xxxxxxxxx>
Signed-off-by: Michel Thierry <michel.thierry@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_gtt.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c
b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 6fae6bd..6d894fc 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -756,8 +756,8 @@ static int
gen8_ppgtt_alloc_page_directories(struct i915_hw_ppgtt *ppgtt,
WARN_ON(!bitmap_empty(new_pds, GEN8_LEGACY_PDPES));
- /* FIXME: PPGTT container_of won't work for 64b */
- WARN_ON((start + length) > 0x800000000ULL);
+ /* FIXME: upper bound must not overflow 31 bits */
+ WARN_ON((start + length) & (~0ULL << 31));
Why is it 31 and not 32?
Right, the check really should be (start + length) >= 0x100000000ULL.
Something with '32' in it might be more obvious and save anyone having
to count the zeroes ... and a comment that also mentioned the limit:
/* FIXME: for now, upper bound must fit in 32 bits */
WARN_ON((start + length) >= (1ULL << 32))
WARN_ON((start + length) & (~0ULL << 32))
WARN_ON((start + length) >> 32) != 0)
Yes, I was planning to just replace _31_ with _32_ and avoid all those
zeroes...
.Dave.
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