Re: [PATCH] drm/amdgpu: make IB test synchronize with init for SRIOV

Christian König <ckoenig.leichtzumerken@xxxxxxxxx> · Mon, 29 Jun 2020 11:09:55 +0200

Am 29.06.20 um 11:03 schrieb Liu, Monk:
We explicitly added the asynchronously IB test for SRIOV to make driver load faster. Why is that now a problem?
Well I didn't notice this change explicitly for SRIOV, at least from the code it is quite a normal change

It's been a while, but if I remember correctly the original motivation 
was to reduce the time we spend in exclusive mode for SRIOV.

Of course bare metal quickly picket this up as well because it reduces 
the time we spend in modprobe.

And why would it help when the VM shuts down? We cancel/flush the test during driver unload/suspend as well.
If you do the sequence like: load amdgpu and shutdown VM immediately , you will hit problems .

Virtual Machine's shutdown won't be blocked if the IB test is on the fly , e.g.: you can do "init 0" right after "modprobe amdgpu" and the "amdgpu_device_fini" won't be called
Thus the flushing on IB test won't happen so the IB test is still running with the VM already shutdown and lead to GPU crash (usually VCN/VCE crash on invalid memory address)

Yeah, that is rather obvious. We try to reduce the modprobe time, but 
this is rather harmful for this test case.

But this can happen with any work running on the GPU. Do we have a 
specific test case for this or why is it a problem?

I mean we should not change the driver just to make a strange QA test 
case work which otherwise never happens in practice.

If we really need this I suggest to just add "if (amdgpu_sriov_vf(adev)) 
flush_delayed_work(&adev->delayed_init_work);" at the end of 
amdgpu_device_init().

Thanks,
Christian.


  
_____________________________________
Monk Liu|GPU Virtualization Team |AMD


-----Original Message-----
From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
Sent: Monday, June 29, 2020 4:18 PM
To: Liu, Monk <Monk.Liu@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [PATCH] drm/amdgpu: make IB test synchronize with init for SRIOV

Am 29.06.20 um 09:11 schrieb Monk Liu:
From: pengzhou <PengJu.Zhou@xxxxxxx>

issue:
originally we kickoff IB test asynchronously with driver's init, thus
the IB test may still running when the driver loading done (modprobe amdgpu done).
if we shutdown VM immediately after amdgpu driver loaded then GPU may
hang because the IB test is still running

fix:
make IB test synchronize with driver init thus it won't still running
when we shutdown the VM.
We explicitly added the asynchronously IB test for SRIOV to make driver load faster. Why is that now a problem?

And why would it help when the VM shuts down? We cancel/flush the test during driver unload/suspend as well.

Signed-off-by: Monk Liu <Monk.Liu@xxxxxxx>
---
   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 29 ++++++++++++++++++++++++-----
   1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 457f5d2..4f54660 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -3292,8 +3292,16 @@ int amdgpu_device_init(struct amdgpu_device *adev,
   	/* must succeed. */
   	amdgpu_ras_resume(adev);
   
-	queue_delayed_work(system_wq, &adev->delayed_init_work,
+	if (amdgpu_sriov_vf(adev)) {
+		r = amdgpu_ib_ring_tests(adev);
+		if (r) {
+			DRM_ERROR("ib ring test failed (%d).\n", r);
+			return r;
+		}
+	} else {
+		queue_delayed_work(system_wq, &adev->delayed_init_work,
   			   msecs_to_jiffies(AMDGPU_RESUME_MS));
+	}
   
   	r = sysfs_create_files(&adev->dev->kobj, amdgpu_dev_attributes);
   	if (r) {
@@ -3329,7 +3337,8 @@ void amdgpu_device_fini(struct amdgpu_device *adev)
   	int r;
   
   	DRM_INFO("amdgpu: finishing device.\n");
-	flush_delayed_work(&adev->delayed_init_work);
+	if (!amdgpu_sriov_vf(adev))
+		flush_delayed_work(&adev->delayed_init_work);
You can drop this change, flushing a work which was never scheduled is harmless.

   	adev->shutdown = true;
   
   	/* make sure IB test finished before entering exclusive mode @@
-3425,7 +3434,8 @@ int amdgpu_device_suspend(struct drm_device *dev, bool fbcon)
   	if (fbcon)
   		amdgpu_fbdev_set_suspend(adev, 1);
   
-	cancel_delayed_work_sync(&adev->delayed_init_work);
+	if (!amdgpu_sriov_vf(adev))
+		cancel_delayed_work_sync(&adev->delayed_init_work);
   
   	if (!amdgpu_device_has_dc_support(adev)) {
   		/* turn off display hw */
@@ -3528,8 +3538,16 @@ int amdgpu_device_resume(struct drm_device *dev, bool fbcon)
   	if (r)
   		return r;
   
-	queue_delayed_work(system_wq, &adev->delayed_init_work,
+	if (amdgpu_sriov_vf(adev)) {
+		r = amdgpu_ib_ring_tests(adev);
+		if (r) {
+			DRM_ERROR("ib ring test failed (%d).\n", r);
+			return r;
+		}
+	} else {
+		queue_delayed_work(system_wq, &adev->delayed_init_work,
   			   msecs_to_jiffies(AMDGPU_RESUME_MS));
+	}
   
   	if (!amdgpu_device_has_dc_support(adev)) {
   		/* pin cursors */
@@ -3554,7 +3572,8 @@ int amdgpu_device_resume(struct drm_device *dev, bool fbcon)
   		return r;
   
   	/* Make sure IB tests flushed */
-	flush_delayed_work(&adev->delayed_init_work);
+	if (!amdgpu_sriov_vf(adev))
+		flush_delayed_work(&adev->delayed_init_work);
   
   	/* blat the mode back in */
   	if (fbcon) {
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