On Thu, Apr 30, 2015 at 03:53:29PM +0100, 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)) This would match the '1ULL<<32' used in the ppgtt init. > WARN_ON((start + length) & (~0ULL << 32)) > WARN_ON((start + length) >> 32) != 0) > > .Dave. -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
