Re: [PATCH 2/5] drm/amdkfd: check child range to drain retry fault

[Felix Kuehling]

On 2021-11-09 6:04 p.m., Philip Yang wrote:
If unmapping partial range, the parent prange list op is update
notifier, child range list op is unmap range, need check child range to
set drain retry fault flag.

Signed-off-by: Philip Yang <philip.y...@amd.com>

I think this could be simplified by simply setting 
svms->drain_pagefaults in svm_range_unmap_from_cpu. The mmap lock 
ensures that this is serialized with the deferred list worker reading 
and clearing svms->drain_pagefaults. You can also use READ_ONCE and 
WRITE_ONCE to be safe.

Regards,
  Felix


---
  drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 13 ++++++++++++-
  1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 77239b06b236..64f642935600 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -2049,8 +2049,19 @@ svm_range_add_list_work(struct svm_range_list *svms, 
struct svm_range *prange,
         * before the range is freed to avoid straggler interrupts on
         * unmapped memory causing "phantom faults".
         */
-       if (op == SVM_OP_UNMAP_RANGE)
+       if (op == SVM_OP_UNMAP_RANGE) {
+               pr_debug("set range drain_pagefaults true\n");
                svms->drain_pagefaults = true;
+       } else {
+               struct svm_range *pchild;
+
+               list_for_each_entry(pchild, &prange->child_list, child_list)
+                       if (pchild->work_item.op == SVM_OP_UNMAP_RANGE) {
+                               pr_debug("set child drain_pagefaults true\n");
+                               svms->drain_pagefaults = true;
+                       }
+       }
+
        /* if prange is on the deferred list */
        if (!list_empty(&prange->deferred_list)) {
                pr_debug("update exist prange 0x%p work op %d\n", prange, op);