On 27/04/2020 10:55, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2020-04-27 10:50:01)
On 27/04/2020 09:40, Chris Wilson wrote:
We see that if the HW doesn't actually sleep, the HW may eat the poison
we set in its write-only HWSP during sanitize:
intel_gt_resume.part.8: 0000:00:02.0
__gt_unpark: 0000:00:02.0
gt_sanitize: 0000:00:02.0 force:yes
process_csb: 0000:00:02.0 vcs0: cs-irq head=5, tail=90
process_csb: 0000:00:02.0 vcs0: csb[0]: status=0x5a5a5a5a:0x5a5a5a5a
assert_pending_valid: Nothing pending for promotion!
The CS TAIL pointer should have been reset by reset_csb_pointers(), so
in this case it is likely that we have read back from the CPU cache and
so we must clflush our control over that page. In doing so, push the
sanitisation to the start of the GT sequence so that our poisoning is
assuredly before we start talking to the HW.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_gt_pm.c | 3 ++-
drivers/gpu/drm/i915/gt/intel_lrc.c | 3 +++
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
index 4c4c74ef4f21..5097786f4375 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
@@ -198,11 +198,12 @@ int intel_gt_resume(struct intel_gt *gt)
* Only the kernel contexts should remain pinned over suspend,
* allowing us to fixup the user contexts on their first pin.
*/
+ gt_sanitize(gt, true);
+
intel_gt_pm_get(gt);
gt_sanitize declares hw access so I thin it should still be after this
pm get.
We control the rpm/uncore access inside gt_sanitize. And the reset we do
there avoid interfering with the gt_pm, so I think this is safe. Note
that the gt_sanitize() we do later is after we release gt_pm. So it
seems reasonable to say that we do it before/after gt_pm.
On the suspend path? Okay.. I guess that proves it works.
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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