drm/i915: Avoid undefined behaviour of "u32 >> 32"
When computing a hash for looking up relocation target handles in an execbuf, we start with a large size for the hashtable and proceed to halve it until the allocation succeeds. The final attempt is with an order of 0 (i.e. a single element). This means that we then pass bits=0 to hash_32() which then computes "hash >> (32 - 0)" to lookup the single element. Right shifting a value by the width of the operand is undefined, so limit the smallest hash table we use to order 1. v2: Keep the retry allocation flag for the final pass Fixes: 4ff4b44c ("drm/i915: Store a direct lookup from object handle to vma") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170629150425.27508-1-chris@chris-wilson.co.uk
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