On Thu, Aug 08, 2013 at 02:37:35PM +0100, Chris Wilson wrote:
The extended state bits are stored in the LCA register and affect all updates to the LCA register - i.e. the state on the old context is saved when SAVE_EX_STATE_EN is currently set in the old context address before the update, and the new context is restored when RESTORE_EX_STATE_EN is set in the new context address. This is irrespective of the RESTORE_INHIBIT flag in the MI_SET_CONTEXT. Hence, upon initial loading the contents of the extended state is read from uninitialised data. To workaround this, on first load we do a dummy load without the mandatory RESTORE_EX_STATE_EN bit so that the real load causes us to initialise the extended state of the context before it is then loaded by the LCA update. References: https://bugs.freedesktop.org/show_bug.cgi?id=64073 Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Ben Widawsky <ben@xxxxxxxxxxxx>
If you split this up in 2, the variable length for mi_set_context, and the workaround - the variable length thing is: Reviewed-by: Ben Widawsky <ben@xxxxxxxxxxxx> I'd like to dig a bit more at the workaround portion. -- Ben Widawsky, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
