On 13/07/2020 17:05, Chris Wilson wrote:
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:
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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