On 25 October 2016 at 00:19, Robert Bragg <robert@xxxxxxxxxxxxx> wrote: > check_cmd() is checking whether a command adheres to certain > restrictions that ensure it's safe to execute within a privileged batch > buffer. Returning false implies a privilege problem, not that the > command is invalid. > > The distinction makes the difference between allowing the buffer to be > executed as an unprivileged batch buffer or returning an EINVAL error to > userspace without executing anything. > > In a case where userspace may want to test whether it can successfully > write to a register that needs privileges the distinction may be > important and an EINVAL error may be considered fatal. > > In particular this is currently true for Mesa, which includes a test for > whether OACONTROL can be written too, but Mesa treats any error when > flushing a batch buffer as fatal, calling exit(1). > > As it is currently Mesa can gracefully handle a failure to write to > OACONTROL if the command parser is disabled, but if we were to remove > OACONTROL from the parser's whitelist then the returned EINVAL would > break Mesa applications as they attempt an OACONTROL write. > > This bumps the command parser version from 7 to 8, as the change is > visible to userspace. > > Signed-off-by: Robert Bragg <robert@xxxxxxxxxxxxx> Seems reasonable. Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx> _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
