Re: [PATCH] drm/amdkfd: drop process ref count when xnack disable

[philip yang <yangp@xxxxxxx>]

On 2021-09-01 9:45 a.m., Kim, Jonathan wrote:

[AMD Official Use Only]

We were seeing process leaks on a couple of machines running certain tests that triggered vm faults on purpose.

I think svm_range_restore_pages gets called unconditionally on vm fault handling (unless the retry interrupt payload bit is supposed to be clear with xnack off)?

 

yes, with xnack off, sh_mem_config retry should be off, retry bit is supposed to be clear in fault interrupt vector, we should not try to recover vm fault, just report the vm fault back to application and evict user queues. Maybe it is another bug cause p->xnack_enabled and sh_mem_config retry mismatch under specific condition?

Regards,

Philip

Either way, this patch prevents the process leaks we seeing and is also:

Reviewed-by: Jonathan Kim <jonathan.kim@xxxxxxx>

 

Thanks,

 

Jon

 

 

From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of philip yang
Sent: Wednesday, September 1, 2021 7:30 AM
To: Sierra Guiza, Alejandro (Alex) <Alex.Sierra@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [PATCH] drm/amdkfd: drop process ref count when xnack disable

 

[CAUTION: External Email]

 

On 2021-08-31 10:41 p.m., Alex Sierra wrote:

During svm restore pages interrupt handler, kfd_process ref count was

never dropped when xnack was disabled. Therefore, the object was never

released.

Good catch, but if xnack is off, we should not get here to recover fault.

The fix looks good to me.

Reviewed-by: Philip Yang <philip.yang@xxxxxxx>

Signed-off-by: Alex Sierra <alex.sierra@xxxxxxx>

---

 drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 3 ++-

 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c

index 8f9b5b53dab5..110c46cd7fac 100644

--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c

+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c

@@ -2484,7 +2484,8 @@ svm_range_restore_pages(struct amdgpu_device *adev, unsigned int pasid,

         }

         if (!p->xnack_enabled) {

                pr_debug("XNACK not enabled for pasid 0x%x\n", pasid);

-               return -EFAULT;

+               r = -EFAULT;

+               goto out;

         }

         svms = &p->svms;