[PATCH v6 1/2] drm/amdgpu: convert amdgpu_vm_lock_by_pasid() to drm_exec
From: Mikhail Gavrilov
Date: Fri May 29 2026 - 02:48:59 EST
amdgpu_vm_lock_by_pasid() looks up a VM by PASID and reserves its root
PD with a bare amdgpu_bo_reserve(), returning the still-reserved root to
the caller. A caller that then needs to reserve further BOs (for example
the devcoredump IB dump) ends up nesting reservation_ww_class_mutex
acquires without a ww_acquire_ctx, which lockdep flags as recursive
locking.
Convert the helper to take a drm_exec context and lock the root PD with
drm_exec_lock_obj(). Callers now run it inside a
drm_exec_until_all_locked() loop and can lock additional BOs in the same
ww ticket, so there is no nested ww_mutex acquire.
The drm_exec context holds its own reference on the locked root BO, so
the helper no longer hands a root reference back to the caller: the
root output parameter is dropped, and the transient reference taken
across the PASID lookup is released before returning.
The only existing caller, amdgpu_vm_handle_fault(), is updated
accordingly. Its is_compute_context path, which previously dropped the
root reservation around svm_range_restore_pages() and re-took it, now
finalises the drm_exec context and re-initialises a fresh one; behaviour
is otherwise unchanged.
No functional change intended for the page-fault path.
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@xxxxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 91 ++++++++++++++++----------
drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 2 +-
2 files changed, 58 insertions(+), 35 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index fccd758b6699..b9d93b664daf 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2950,47 +2950,56 @@ int amdgpu_vm_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
}
/**
- * amdgpu_vm_lock_by_pasid - return an amdgpu_vm and its root bo from a pasid, if possible.
+ * amdgpu_vm_lock_by_pasid - look up a VM by PASID and lock its root PD
* @adev: amdgpu device pointer
- * @root: root BO of the VM
* @pasid: PASID of the VM
- * The caller needs to unreserve and unref the root bo on success.
+ * @exec: drm_exec context to lock the root PD in
+ *
+ * Must be called from within a drm_exec_until_all_locked() loop; the caller
+ * runs drm_exec_retry_on_contention() afterwards. The drm_exec context holds
+ * a reference on the root BO until it is finalised.
+ *
+ * Return: the VM on success, or NULL if the PASID has no VM, the VM is being
+ * torn down, or locking the root PD failed.
*/
struct amdgpu_vm *amdgpu_vm_lock_by_pasid(struct amdgpu_device *adev,
- struct amdgpu_bo **root, u32 pasid)
+ u32 pasid, struct drm_exec *exec)
{
unsigned long irqflags;
+ struct amdgpu_bo *root;
struct amdgpu_vm *vm;
int r;
xa_lock_irqsave(&adev->vm_manager.pasids, irqflags);
vm = xa_load(&adev->vm_manager.pasids, pasid);
- *root = vm ? amdgpu_bo_ref(vm->root.bo) : NULL;
+ root = vm ? amdgpu_bo_ref(vm->root.bo) : NULL;
xa_unlock_irqrestore(&adev->vm_manager.pasids, irqflags);
- if (!*root)
+ if (!root)
return NULL;
- r = amdgpu_bo_reserve(*root, true);
- if (r)
- goto error_unref;
+ r = drm_exec_lock_obj(exec, &root->tbo.base);
+ if (r) {
+ amdgpu_bo_unref(&root);
+ return NULL;
+ }
/* Double check that the VM still exists */
xa_lock_irqsave(&adev->vm_manager.pasids, irqflags);
vm = xa_load(&adev->vm_manager.pasids, pasid);
- if (vm && vm->root.bo != *root)
+ if (vm && vm->root.bo != root)
vm = NULL;
xa_unlock_irqrestore(&adev->vm_manager.pasids, irqflags);
- if (!vm)
- goto error_unlock;
+ if (!vm) {
+ drm_exec_unlock_obj(exec, &root->tbo.base);
+ amdgpu_bo_unref(&root);
+ return NULL;
+ }
- return vm;
-error_unlock:
- amdgpu_bo_unreserve(*root);
+ /* The drm_exec context holds its own reference on the root BO. */
+ amdgpu_bo_unref(&root);
-error_unref:
- amdgpu_bo_unref(root);
- return NULL;
+ return vm;
}
/**
@@ -3012,33 +3021,49 @@ bool amdgpu_vm_handle_fault(struct amdgpu_device *adev, u32 pasid,
uint64_t ts, bool write_fault)
{
bool is_compute_context = false;
- struct amdgpu_bo *root;
+ struct drm_exec exec;
uint64_t value, flags;
struct amdgpu_vm *vm;
int r;
- vm = amdgpu_vm_lock_by_pasid(adev, &root, pasid);
- if (!vm)
+ drm_exec_init(&exec, 0, 1);
+ drm_exec_until_all_locked(&exec) {
+ vm = amdgpu_vm_lock_by_pasid(adev, pasid, &exec);
+ drm_exec_retry_on_contention(&exec);
+ if (!vm)
+ break;
+ }
+ if (!vm) {
+ drm_exec_fini(&exec);
return false;
+ }
is_compute_context = vm->is_compute_context;
if (is_compute_context) {
- /* Unreserve root since svm_range_restore_pages might try to reserve it. */
- /* TODO: rework svm_range_restore_pages so that this isn't necessary. */
- amdgpu_bo_unreserve(root);
+ /* Release the root PD lock since svm_range_restore_pages
+ * might try to take it.
+ * TODO: rework svm_range_restore_pages so that this isn't
+ * necessary.
+ */
+ drm_exec_fini(&exec);
if (!svm_range_restore_pages(adev, pasid, vmid,
- node_id, addr >> PAGE_SHIFT, ts, write_fault)) {
- amdgpu_bo_unref(&root);
+ node_id, addr >> PAGE_SHIFT, ts, write_fault))
return true;
- }
- amdgpu_bo_unref(&root);
/* Re-acquire the VM lock, could be that the VM was freed in between. */
- vm = amdgpu_vm_lock_by_pasid(adev, &root, pasid);
- if (!vm)
+ drm_exec_init(&exec, 0, 1);
+ drm_exec_until_all_locked(&exec) {
+ vm = amdgpu_vm_lock_by_pasid(adev, pasid, &exec);
+ drm_exec_retry_on_contention(&exec);
+ if (!vm)
+ break;
+ }
+ if (!vm) {
+ drm_exec_fini(&exec);
return false;
+ }
}
addr /= AMDGPU_GPU_PAGE_SIZE;
@@ -3062,7 +3087,7 @@ bool amdgpu_vm_handle_fault(struct amdgpu_device *adev, u32 pasid,
value = 0;
}
- r = dma_resv_reserve_fences(root->tbo.base.resv, 1);
+ r = dma_resv_reserve_fences(vm->root.bo->tbo.base.resv, 1);
if (r) {
pr_debug("failed %d to reserve fence slot\n", r);
goto error_unlock;
@@ -3076,12 +3101,10 @@ bool amdgpu_vm_handle_fault(struct amdgpu_device *adev, u32 pasid,
r = amdgpu_vm_update_pdes(adev, vm, true);
error_unlock:
- amdgpu_bo_unreserve(root);
+ drm_exec_fini(&exec);
if (r < 0)
dev_err(adev->dev, "Can't handle page fault (%d)\n", r);
- amdgpu_bo_unref(&root);
-
return false;
}
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
index d083d7aab75c..0c6e3e0368c7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
@@ -593,7 +593,7 @@ bool amdgpu_vm_handle_fault(struct amdgpu_device *adev, u32 pasid,
bool write_fault);
struct amdgpu_vm *amdgpu_vm_lock_by_pasid(struct amdgpu_device *adev,
- struct amdgpu_bo **root, u32 pasid);
+ u32 pasid, struct drm_exec *exec);
void amdgpu_vm_set_task_info(struct amdgpu_vm *vm);
--
2.54.0