On 2023-10-03 16:50, Philip Yang wrote:
If there is no VRAM domain, bo_node is NULL and this causes crash.
Refactor the change, and use the module parameter as higher privilege.

Need another patch to support override PTE flag on APU.

Fixes: 55d7e2001c7e ("drm/amdgpu: Add EXT_COHERENT memory allocation flags")
Signed-off-by: Philip Yang <[email protected]>
---
  drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 18 +++++++-----------
  1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 0d88698ae33f..305b2c54edfa 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -1248,26 +1248,22 @@ svm_range_get_pte_flags(struct kfd_node *node,
                break;
        case IP_VERSION(9, 4, 3):
                mtype_local = amdgpu_mtype_local == 1 ? AMDGPU_VM_MTYPE_NC :
-                            (amdgpu_mtype_local == 2 ? AMDGPU_VM_MTYPE_CC : 
AMDGPU_VM_MTYPE_RW);
+                             (amdgpu_mtype_local == 2 || ext_coherent ?
+                                       AMDGPU_VM_MTYPE_CC : 
AMDGPU_VM_MTYPE_RW);

We had some offline discussion where I thought that MTYPE_NC should become MTYPE_UC when ext_coherent is enabled to get the desired memory semantics. With that idea in mind, this would become a bit more messy, but here it goes, as clean as I can make it:

-               mtype_local = amdgpu_mtype_local == 1 ? AMDGPU_VM_MTYPE_NC :
-                            (amdgpu_mtype_local == 2 ? AMDGPU_VM_MTYPE_CC : 
AMDGPU_VM_MTYPE_RW);
+               mtype_local = amdgpu_mtype_local == 1 && !ext_coherent ? 
AMDGPU_VM_MTYPE_NC :
+                            (amdgpu_mtype_local == 1 &&  ext_coherent ? 
AMDGPU_VM_MTYPE_UC :
+                            (amdgpu_mtype_local == 2 ||  ext_coherent ? 
AMDGPU_VM_MTYPE_CC :
+                                                                        
AMDGPU_VM_MTYPE_RW));

But maybe that could be fixed up in a follow up patch. Either way, for the purpose of fixing the crash, this patch is

Reviewed-by: Felix Kuehling <[email protected]>


                snoop = true;
                if (uncached) {
                        mapping_flags |= AMDGPU_VM_MTYPE_UC;
-               } else if (ext_coherent) {
-                       /* local HBM region close to partition */
-                       if (bo_node->adev == node->adev &&
-                           (!bo_node->xcp || !node->xcp || bo_node->xcp->mem_id == 
node->xcp->mem_id))
-                               mapping_flags |= AMDGPU_VM_MTYPE_CC;
-                       else
-                               mapping_flags |= AMDGPU_VM_MTYPE_UC;
                } else if (domain == SVM_RANGE_VRAM_DOMAIN) {
                        /* local HBM region close to partition */
                        if (bo_node->adev == node->adev &&
                            (!bo_node->xcp || !node->xcp || bo_node->xcp->mem_id == 
node->xcp->mem_id))
                                mapping_flags |= mtype_local;
-                       /* local HBM region far from partition or remote XGMI 
GPU */
-                       else if (svm_nodes_in_same_hive(bo_node, node))
+                       /* local HBM region far from partition or remote XGMI 
GPU
+                        * with regular system scope coherence
+                        */
+                       else if (svm_nodes_in_same_hive(bo_node, node) && 
!ext_coherent)
                                mapping_flags |= AMDGPU_VM_MTYPE_NC;
-                       /* PCIe P2P */
+                       /* PCIe P2P or extended system scope coherence */
                        else
                                mapping_flags |= AMDGPU_VM_MTYPE_UC;
                /* system memory accessed by the APU */

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