[PATCH v4 01/30] drm/xe: Lock all gpuva ops during VM bind IOCTL
Zeng, Oak
oak.zeng at intel.com
Sun Mar 10 17:44:00 UTC 2024
> -----Original Message-----
> From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of Matthew
> Brost
> Sent: Friday, March 8, 2024 12:08 AM
> To: intel-xe at lists.freedesktop.org
> Cc: Brost, Matthew <matthew.brost at intel.com>
> Subject: [PATCH v4 01/30] drm/xe: Lock all gpuva ops during VM bind IOCTL
>
> Lock all gpuva ops
Can we have a better wording? Better to say locking all Bos used in gpuva ops?
Or maybe lock ops by locking and validating all Bos used in ops.
and validate all BOs in a single step durin the VM
> bind IOCTL. This help with the transition to making all gpuva ops in a
> VM bind IOCTL a single atomic job.
Can you also explain, why you want bind to be a atomic job?
My guess is, bind ioctl can end up with a series of operations, if some (not all) of those operations fail in the middle, it is hard to revert the successful operations before failure.
>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
> drivers/gpu/drm/xe/xe_vm.c | 142 ++++++++++++++++++++++++++-----------
> 1 file changed, 101 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 643b3701a738..3b5dc6de07f7 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -413,19 +413,23 @@ int __xe_vm_userptr_needs_repin(struct xe_vm *vm)
>
> #define XE_VM_REBIND_RETRY_TIMEOUT_MS 1000
>
> -static void xe_vm_kill(struct xe_vm *vm)
> +static void xe_vm_kill(struct xe_vm *vm, bool unlocked)
> {
> struct xe_exec_queue *q;
>
> lockdep_assert_held(&vm->lock);
>
> - xe_vm_lock(vm, false);
> + if (unlocked)
> + xe_vm_lock(vm, false);
> +
Can you explain why we need xe_vm_lock in the first place here?
My understanding is, xe_vm_lock protect gpu page table update. Below kill function eventually calls into guc_exec_queue_kill where I don't see any page table operation there. So I doubt whether we need the lock in the first place.
> vm->flags |= XE_VM_FLAG_BANNED;
> trace_xe_vm_kill(vm);
>
> list_for_each_entry(q, &vm->preempt.exec_queues, compute.link)
> q->ops->kill(q);
> - xe_vm_unlock(vm);
> +
> + if (unlocked)
> + xe_vm_unlock(vm);
>
> /* TODO: Inform user the VM is banned */
> }
> @@ -621,7 +625,7 @@ static void preempt_rebind_work_func(struct work_struct
> *w)
>
> if (err) {
> drm_warn(&vm->xe->drm, "VM worker error: %d\n", err);
> - xe_vm_kill(vm);
> + xe_vm_kill(vm, true);
> }
> up_write(&vm->lock);
>
> @@ -1831,17 +1835,9 @@ static int xe_vm_bind(struct xe_vm *vm, struct xe_vma
> *vma, struct xe_exec_queue
> u32 num_syncs, bool immediate, bool first_op,
> bool last_op)
> {
> - int err;
> -
> xe_vm_assert_held(vm);
> xe_bo_assert_held(bo);
>
> - if (bo && immediate) {
> - err = xe_bo_validate(bo, vm, true);
> - if (err)
> - return err;
> - }
> -
> return __xe_vm_bind(vm, vma, q, syncs, num_syncs, immediate, first_op,
> last_op);
> }
> @@ -2488,17 +2484,12 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm,
> struct xe_exec_queue *q,
> return 0;
> }
>
> -static int op_execute(struct drm_exec *exec, struct xe_vm *vm,
> - struct xe_vma *vma, struct xe_vma_op *op)
> +static int op_execute(struct xe_vm *vm, struct xe_vma *vma,
> + struct xe_vma_op *op)
> {
> int err;
>
> lockdep_assert_held_write(&vm->lock);
> -
> - err = xe_vm_prepare_vma(exec, vma, 1);
> - if (err)
> - return err;
> -
> xe_vm_assert_held(vm);
> xe_bo_assert_held(xe_vma_bo(vma));
>
> @@ -2579,19 +2570,10 @@ static int op_execute(struct drm_exec *exec, struct
> xe_vm *vm,
> static int __xe_vma_op_execute(struct xe_vm *vm, struct xe_vma *vma,
> struct xe_vma_op *op)
> {
> - struct drm_exec exec;
> int err;
>
> retry_userptr:
> - drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT, 0);
> - drm_exec_until_all_locked(&exec) {
> - err = op_execute(&exec, vm, vma, op);
> - drm_exec_retry_on_contention(&exec);
> - if (err)
> - break;
> - }
> - drm_exec_fini(&exec);
> -
> + err = op_execute(vm, vma, op);
> if (err == -EAGAIN) {
> lockdep_assert_held_write(&vm->lock);
>
> @@ -2756,29 +2738,107 @@ static void vm_bind_ioctl_ops_unwind(struct xe_vm
> *vm,
> }
> }
>
> +static int vma_lock(struct drm_exec *exec, struct xe_vma *vma, bool validate)
> +{
> + struct xe_bo *bo = xe_vma_bo(vma);
> + int err = 0;
> +
> + if (bo) {
> + if (!bo->vm)
> + err = drm_exec_prepare_obj(exec, &bo->ttm.base, 1);
> + if (!err && validate)
> + err = xe_bo_validate(bo, xe_vma_vm(vma), true);
> + }
> +
> + return err;
> +}
> +
> +static int op_lock(struct drm_exec *exec, struct xe_vm *vm,
> + struct xe_vma_op *op)
> +{
> + int err = 0;
> +
> + switch (op->base.op) {
> + case DRM_GPUVA_OP_MAP:
> + err = vma_lock(exec, op->map.vma, !xe_vm_in_fault_mode(vm));
> + break;
> + case DRM_GPUVA_OP_REMAP:
> + err = vma_lock(exec, gpuva_to_vma(op->base.remap.unmap->va),
> + false);
> + if (!err && op->remap.prev)
> + err = vma_lock(exec, op->remap.prev, true);
> + if (!err && op->remap.next)
> + err = vma_lock(exec, op->remap.next, true);
> + break;
> + case DRM_GPUVA_OP_UNMAP:
> + err = vma_lock(exec, gpuva_to_vma(op->base.unmap.va), false);
> + break;
> + case DRM_GPUVA_OP_PREFETCH:
> + err = vma_lock(exec, gpuva_to_vma(op->base.prefetch.va), true);
> + break;
> + default:
> + drm_warn(&vm->xe->drm, "NOT POSSIBLE");
> + }
> +
> + return err;
> +}
> +
> +static int vm_bind_ioctl_ops_lock(struct drm_exec *exec,
> + struct xe_vm *vm,
> + struct list_head *ops_list)
> +{
> + struct xe_vma_op *op;
> + int err;
> +
> + err = drm_exec_prepare_obj(exec, xe_vm_obj(vm), 1);
> + if (err)
> + return err;
> +
> + list_for_each_entry(op, ops_list, link) {
> + err = op_lock(exec, vm, op);
> + if (err)
> + return err;
> + }
> +
> + return 0;
> +}
> +
> static int vm_bind_ioctl_ops_execute(struct xe_vm *vm,
> struct list_head *ops_list)
> {
> + struct drm_exec exec;
> struct xe_vma_op *op, *next;
> int err;
>
> lockdep_assert_held_write(&vm->lock);
>
> - list_for_each_entry_safe(op, next, ops_list, link) {
> - err = xe_vma_op_execute(vm, op);
> - if (err) {
> - drm_warn(&vm->xe->drm, "VM op(%d) failed with %d",
> - op->base.op, err);
> - /*
> - * FIXME: Killing VM rather than proper error handling
> - */
> - xe_vm_kill(vm);
> - return -ENOSPC;
> + drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT |
> + DRM_EXEC_IGNORE_DUPLICATES, 0);
> + drm_exec_until_all_locked(&exec) {
> + err = vm_bind_ioctl_ops_lock(&exec, vm, ops_list);
> + drm_exec_retry_on_contention(&exec);
> + if (err)
> + goto unlock;
> +
Do you need below ops inside the drm_exec_until_all_locked loop? After you locked all objects, you can close the drm_exec_until_all_locked loop, then perform below out of drm_exec_until_all_locked loop.
Oak
> + list_for_each_entry_safe(op, next, ops_list, link) {
> + err = xe_vma_op_execute(vm, op);
> + if (err) {
> + drm_warn(&vm->xe->drm, "VM op(%d) failed
> with %d",
> + op->base.op, err);
> + /*
> + * FIXME: Killing VM rather than proper error
> handling
> + */
> + xe_vm_kill(vm, false);
> + err = -ENOSPC;
> + goto unlock;
> + }
> + xe_vma_op_cleanup(vm, op);
> }
> - xe_vma_op_cleanup(vm, op);
> }
>
> - return 0;
> +unlock:
> + drm_exec_fini(&exec);
> + return err;
> }
>
> #define SUPPORTED_FLAGS (DRM_XE_VM_BIND_FLAG_NULL | \
> --
> 2.34.1
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