Add a way for userspace to specify the sequence number fence used to
track completion of the submit. As the seqno fence is simply an
incrementing counter which is local to the submitqueue, it is easy for
userspace to know the next value.
This is useful for native userspace drivers in a vm guest, as the guest
to host roundtrip can have high latency. Assigning the fence seqno in
the guest userspace allows the guest to continue without waiting for
response from the host.
Signed-off-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20220224222321.60653-1-robdclark@gmail.com
17154addc5