[Intel-gfx] [PATCH] drm/i915: Seal busy-ioctl uABI and prevent leaking of internal ids

[Tvrtko Ursulin]

On 15/01/16 13:57, Chris Wilson wrote:
> On Fri, Jan 15, 2016 at 01:22:39PM +0000, Tvrtko Ursulin wrote:
>> Looks like your DDX is the only user not using it in the boolean mode?
>
> As far as I am aware, that is the only user that worries about which
> engine the object is currently active on.
>
>> And libdrm is a bit confused in its return statements:
>>
>>          ret = drmIoctl(bufmgr_gem->fd, DRM_IOCTL_I915_GEM_BUSY, &busy);
>>          if (ret == 0) {
>>                  bo_gem->idle = !busy.busy;
>>                  return busy.busy;
>>          } else {
>>                  return false;
>>          }
>>          return (ret == 0 && busy.busy);
>>
>> Looks like it was a boolean as well until commit
>> 02f93c21e6e1c3dad9d99349989daa84a8c0b5fb quite possibly by accident
>> started exposing the bits.
>
> Hmm, libdrm bo_is_busy() was always meant to be boolean and that patch
> postdates when we started storing read/write bits in the return value.
> So definitely an unintentional leakage.

In that case I think just respin with comment corrections in uapi header 
for drm_i915_gem_busy?

Regards,

Tvrtko