Re: [PATCH v5 3/6] drm/xe/xe_vm: Add per VM pagefault info

[Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx>]

On 3/4/25 7:08 PM, Jonathan Cavitt wrote:
> Add additional information to each VM so they can report up to the last
> 50 seen pagefaults.  Only failed pagefaults are saved this way, as
> successful pagefaults should recover and not need to be reported to
> userspace.
The unrecoverable pagefault scenario causes a caterr or context reset. 
so It would be enough to store one uncoverable pagefault for providing a 
unrecoverable pagefault details to userspace. how do you think?

G.G.

> Signed-off-by: Jonathan Cavitt <jonathan.cavitt@xxxxxxxxx>
> Suggested-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> ---
>   drivers/gpu/drm/xe/xe_gt_pagefault.c | 17 +++++++++++
>   drivers/gpu/drm/xe/xe_vm.c           | 45 ++++++++++++++++++++++++++++
>   drivers/gpu/drm/xe/xe_vm.h           |  6 ++++
>   drivers/gpu/drm/xe/xe_vm_types.h     | 20 +++++++++++++
>   4 files changed, 88 insertions(+)
>
> diff --git a/drivers/gpu/drm/xe/xe_gt_pagefault.c b/drivers/gpu/drm/xe/xe_gt_pagefault.c
> index 07b52d3c1a60..84907fb4295e 100644
> --- a/drivers/gpu/drm/xe/xe_gt_pagefault.c
> +++ b/drivers/gpu/drm/xe/xe_gt_pagefault.c
> @@ -335,6 +335,22 @@ int xe_guc_pagefault_handler(struct xe_guc *guc, u32 *msg, u32 len)
>   	return full ? -ENOSPC : 0;
>   }
>   
> +static void save_pagefault_to_vm(struct xe_device *xe, struct xe_pagefault *pf)
> +{
> +	struct xe_vm *vm;
> +	struct xe_pagefault *store;
> +
> +	vm = asid_to_vm(xe, pf->asid);
> +	if (IS_ERR(vm))
> +		return;
> +
> +	spin_lock(&vm->pfs.lock);
> +	store = kzalloc(sizeof(*pf), GFP_KERNEL);
> +	memcpy(store, pf, sizeof(*pf));
> +	xe_vm_add_pf_entry(vm, store);
> +	spin_unlock(&vm->pfs.lock);
> +}
> +
>   #define USM_QUEUE_MAX_RUNTIME_MS	20
>   
>   static void pf_queue_work_func(struct work_struct *w)
> @@ -353,6 +369,7 @@ static void pf_queue_work_func(struct work_struct *w)
>   		ret = handle_pagefault(gt, &pf);
>   		if (unlikely(ret)) {
>   			print_pagefault(xe, &pf);
> +			save_pagefault_to_vm(xe, &pf);
>   			pf.fault_unsuccessful = 1;
>   			drm_dbg(&xe->drm, "Fault response: Unsuccessful %d\n", ret);
>   		}
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 996000f2424e..6211b971bbbd 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -746,6 +746,46 @@ int xe_vm_userptr_check_repin(struct xe_vm *vm)
>   		list_empty_careful(&vm->userptr.invalidated)) ? 0 : -EAGAIN;
>   }
>   
> +static void free_pf_entry(struct xe_vm *vm, struct xe_vm_pf_entry *e)
> +{
> +	list_del(&e->list);
> +	kfree(e->pf);
> +	kfree(e);
> +	vm->pfs.len--;
> +}
> +
> +void xe_vm_add_pf_entry(struct xe_vm *vm, struct xe_pagefault *pf)
> +{
> +	struct xe_vm_pf_entry *e = NULL;
> +
> +	e = kzalloc(sizeof(*e), GFP_KERNEL);
> +	xe_assert(vm->xe, e);
> +
> +	spin_lock(&vm->pfs.lock);
> +	list_add_tail(&e->list, &vm->pfs.list);
> +	vm->pfs.len++;
> +	/**
> +	 * Limit the number of pfs in the pf list to prevent memory overuse.
> +	 */
> +	if (vm->pfs.len > MAX_PFS) {
> +		struct xe_vm_pf_entry *rem =
> +			list_first_entry(&vm->pfs.list, struct xe_vm_pf_entry, list);
> +
> +		free_pf_entry(vm, rem);
> +	}
> +	spin_unlock(&vm->pfs.lock);
> +}
> +
> +void xe_vm_remove_pf_entries(struct xe_vm *vm)
> +{
> +	struct xe_vm_pf_entry *e, *tmp;
> +
> +	spin_lock(&vm->pfs.lock);
> +	list_for_each_entry_safe(e, tmp, &vm->pfs.list, list)
> +		free_pf_entry(vm, e);
> +	spin_unlock(&vm->pfs.lock);
> +}
> +
>   static int xe_vma_ops_alloc(struct xe_vma_ops *vops, bool array_of_binds)
>   {
>   	int i;
> @@ -1448,6 +1488,9 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags)
>   	init_rwsem(&vm->userptr.notifier_lock);
>   	spin_lock_init(&vm->userptr.invalidated_lock);
>   
> +	INIT_LIST_HEAD(&vm->pfs.list);
> +	spin_lock_init(&vm->pfs.lock);
> +
>   	ttm_lru_bulk_move_init(&vm->lru_bulk_move);
>   
>   	INIT_WORK(&vm->destroy_work, vm_destroy_work_func);
> @@ -1672,6 +1715,8 @@ void xe_vm_close_and_put(struct xe_vm *vm)
>   	}
>   	up_write(&xe->usm.lock);
>   
> +	xe_vm_remove_pf_entries(vm);
> +
>   	for_each_tile(tile, xe, id)
>   		xe_range_fence_tree_fini(&vm->rftree[id]);
>   
> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
> index f66075f8a6fe..4d94ab5c8ea4 100644
> --- a/drivers/gpu/drm/xe/xe_vm.h
> +++ b/drivers/gpu/drm/xe/xe_vm.h
> @@ -12,6 +12,8 @@
>   #include "xe_map.h"
>   #include "xe_vm_types.h"
>   
> +#define MAX_PFS 50
> +
>   struct drm_device;
>   struct drm_printer;
>   struct drm_file;
> @@ -244,6 +246,10 @@ int xe_vma_userptr_pin_pages(struct xe_userptr_vma *uvma);
>   
>   int xe_vma_userptr_check_repin(struct xe_userptr_vma *uvma);
>   
> +void xe_vm_add_pf_entry(struct xe_vm *vm, struct xe_pagefault *pf);
> +
> +void xe_vm_remove_pf_entries(struct xe_vm *vm);
> +
>   bool xe_vm_validate_should_retry(struct drm_exec *exec, int err, ktime_t *end);
>   
>   int xe_vm_lock_vma(struct drm_exec *exec, struct xe_vma *vma);
> diff --git a/drivers/gpu/drm/xe/xe_vm_types.h b/drivers/gpu/drm/xe/xe_vm_types.h
> index 52467b9b5348..10b0952db56c 100644
> --- a/drivers/gpu/drm/xe/xe_vm_types.h
> +++ b/drivers/gpu/drm/xe/xe_vm_types.h
> @@ -18,6 +18,7 @@
>   #include "xe_range_fence.h"
>   
>   struct xe_bo;
> +struct xe_pagefault;
>   struct xe_sync_entry;
>   struct xe_user_fence;
>   struct xe_vm;
> @@ -135,6 +136,13 @@ struct xe_userptr_vma {
>   
>   struct xe_device;
>   
> +struct xe_vm_pf_entry {
> +	/** @pf: observed pagefault */
> +	struct xe_pagefault *pf;
> +	/** @list: link into @xe_vm.pfs.list */
> +	struct list_head list;
> +};
> +
>   struct xe_vm {
>   	/** @gpuvm: base GPUVM used to track VMAs */
>   	struct drm_gpuvm gpuvm;
> @@ -274,6 +282,18 @@ struct xe_vm {
>   		bool capture_once;
>   	} error_capture;
>   
> +	/**
> +	 * @pfs: List of all pagefaults associated with this VM
> +	 */
> +	struct {
> +		/** @lock: lock protecting @bans.list */
> +		spinlock_t lock;
> +		/** @list: list of xe_exec_queue_ban_entry entries */
> +		struct list_head list;
> +		/** @len: length of @bans.list */
> +		unsigned int len;
> +	} pfs;
> +
>   	/**
>   	 * @tlb_flush_seqno: Required TLB flush seqno for the next exec.
>   	 * protected by the vm resv.