[Intel-gfx] [PATCH igt v2] lib: Skip aliased bsd ABI ring if bsd2 is available

[Tvrtko Ursulin]

On 21/02/2018 13:35, Tvrtko Ursulin wrote:
> 
> On 21/02/2018 13:07, Chris Wilson wrote:
>> Quoting Tvrtko Ursulin (2018-02-21 12:55:17)
>>>
>>> On 21/02/2018 12:53, Tvrtko Ursulin wrote:
>>>>
>>>> On 21/02/2018 12:17, Chris Wilson wrote:
>>>>> How much do I want this uABI to rot away? Say "Never again!" to 
>>>>> implicit
>>>>> aliasing.
>>>>>
>>>>> In the meantime, we do not need to perform duplicate work on bsd2
>>>>> machines, as especially we do not know which engine bsd relates to.
>>>>>
>>>>> v2: When in doubt, shout!
>>>>>
>>>>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>>>>> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>>>>> ---
>>>>>    lib/ioctl_wrappers.c | 2 +-
>>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/lib/ioctl_wrappers.c b/lib/ioctl_wrappers.c
>>>>> index 8748cfcf..b9b86079 100644
>>>>> --- a/lib/ioctl_wrappers.c
>>>>> +++ b/lib/ioctl_wrappers.c
>>>>> @@ -1460,7 +1460,7 @@ bool gem_has_ring(int fd, unsigned ring)
>>>>>        /* silly ABI, the kernel thinks everyone who has BSD also has
>>>>> BSD2 */
>>>>>        if ((ring & ~(3<<13)) == I915_EXEC_BSD) {
>>>>> -        if (ring & (3 << 13) && !gem_has_bsd2(fd))
>>>>> +        if (!(ring & (3 << 13)) ^ !gem_has_bsd2(fd))
>>>>>                return false;
>>>>>        }

For preserving time and sanity:

bool is_bsd = (ring & 0xf) == I915_EXEC_BSD;
bool implicit_bsd = !(ring & (3 << 13));
bool supports_explicit_bsd = gem_has_bsd2(fd);

if (is_bsd) {
	if (implicit_bsd && supports_explicit_bsd)
		return false;
	else if (!implicit_bsd && !supports_explicit_bsd)
		return false;
}

?

Regards,

Tvrtko