The danger in switching at random upon intel_context_pin is that the context may still actually be inflight, as it will not be scheduled out until a context switch after it is complete -- that is after we do a final intel_context_unpin. Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2118 Fixes: 6d06779e8672 ("drm/i915: Load balancing across a virtual engine") Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> # v5.3+ --- drivers/gpu/drm/i915/gt/intel_lrc.c | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index cd4262cc96e2..f4658849b08a 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -5435,13 +5435,8 @@ static void virtual_engine_initial_hint(struct virtual_engine *ve) * typically be the first we inspect for submission. */ swp = prandom_u32_max(ve->num_siblings); - if (!swp) - return; - - swap(ve->siblings[swp], ve->siblings[0]); - if (!intel_engine_has_relative_mmio(ve->siblings[0])) - virtual_update_register_offsets(ve->context.lrc_reg_state, - ve->siblings[0]); + if (swp) + swap(ve->siblings[swp], ve->siblings[0]); } static int virtual_context_alloc(struct intel_context *ce) @@ -5454,15 +5449,9 @@ static int virtual_context_alloc(struct intel_context *ce) static int virtual_context_pin(struct intel_context *ce) { struct virtual_engine *ve = container_of(ce, typeof(*ve), context); - int err; /* Note: we must use a real engine class for setting up reg state */ - err = __execlists_context_pin(ce, ve->siblings[0]); - if (err) - return err; - - virtual_engine_initial_hint(ve); - return 0; + return __execlists_context_pin(ce, ve->siblings[0]); } static void virtual_context_enter(struct intel_context *ce) @@ -5808,6 +5797,7 @@ intel_execlists_create_virtual(struct intel_engine_cs **siblings, ve->base.flags |= I915_ENGINE_IS_VIRTUAL; + virtual_engine_initial_hint(ve); return &ve->context; err_put: -- 2.20.1
