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 <ch...@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursu...@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;
}
If default BSD (1)
and no BSD2 -> 1 ^ 1 = 1 OK
Oops
1 ^ 1 = 0 so also bad
and BSD2 -> 1 ^ 0 = 1 BAD
If explicit BSD (0)
and no BSD2 -> 0 ^ 1 = 1 BAD
has BSD2 -> 0 ^ 0 = 0 = BAD
Maybe I'm confused.. please simplify the statement? :)
return false?
default BSD ^ has-bsd2
0 0 -> 0 OK
0 1 -> 1 SKIP
1 0 -> 1 SKIP
1 1 -> 0 OK
So we only use bsd (implicit) on single BSD engine machines, and only
use bsd0,bsd1 (explicit) on dual engine machines.
Don't get in your notation why is 0 OK and 1 SKIP. 0 is false = no ring
= skip.
default BSD ^ has-bsd2
0 0 0 ^ !0 = 1 has engine - WRONG
0 1 0 ^ !1 = 0 no engine - WRONG
1 0 1 ^ !0 = 0 no engine - WRONG
1 1 1 ^ !1 = 1 has engine - WRONG
default BSD ^ has-bsd2
0 0 0 ^ 0 = 0 no engine - OK
0 1 0 ^ 1 = 1 has engine - OK
1 0 1 ^ 0 = 1 has engine - OK
1 1 1 ^ 1 = 0 no engine - OK
So previous version was OK!?
Regards,
Tvrtko
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