-----Original Message-----
From: Brost, Matthew <[email protected]>
Sent: Monday, December 1, 2025 11:18 AM
To: Cavitt, Jonathan <[email protected]>
Cc: [email protected]; Gupta, saurabhg <[email protected]>;
Zuo, Alex <[email protected]>; [email protected]; Zhang, Jianxun
<[email protected]>; Lin, Shuicheng <[email protected]>;
[email protected]; Wajdeczko, Michal
<[email protected]>; Mrozek, Michal <[email protected]>; Jadav,
Raag <[email protected]>; [email protected]; Briano, Ivan
<[email protected]>; Auld, Matthew <[email protected]>; Hirschfeld,
Dafna <[email protected]>
Subject: Re: [PATCH v27 3/4] drm/xe/xe_vm: Add per VM fault info
>
> On Mon, Dec 01, 2025 at 05:44:47PM +0000, Jonathan Cavitt wrote:
> > Add additional information to each VM so they can report up to the first
> > 50 seen faults. Only pagefaults are saved this way currently, though in
> > the future, all faults should be tracked by the VM for future reporting.
> >
> > Additionally, of the pagefaults reported, only failed pagefaults are
> > saved this way, as successful pagefaults should recover silently and not
> > need to be reported to userspace.
> >
> > v2:
> > - Free vm after use (Shuicheng)
> > - Compress pf copy logic (Shuicheng)
> > - Update fault_unsuccessful before storing (Shuicheng)
> > - Fix old struct name in comments (Shuicheng)
> > - Keep first 50 pagefaults instead of last 50 (Jianxun)
> >
> > v3:
> > - Avoid unnecessary execution by checking MAX_PFS earlier (jcavitt)
> > - Fix double-locking error (jcavitt)
> > - Assert kmemdump is successful (Shuicheng)
> >
> > v4:
> > - Rename xe_vm.pfs to xe_vm.faults (jcavitt)
> > - Store fault data and not pagefault in xe_vm faults list (jcavitt)
> > - Store address, address type, and address precision per fault (jcavitt)
> > - Store engine class and instance data per fault (Jianxun)
> > - Add and fix kernel docs (Michal W)
> > - Properly handle kzalloc error (Michal W)
> > - s/MAX_PFS/MAX_FAULTS_SAVED_PER_VM (Michal W)
> > - Store fault level per fault (Micahl M)
> >
> > v5:
> > - Store fault and access type instead of address type (Jianxun)
> >
> > v6:
> > - Store pagefaults in non-fault-mode VMs as well (Jianxun)
> >
> > v7:
> > - Fix kernel docs and comments (Michal W)
> >
> > v8:
> > - Fix double-locking issue (Jianxun)
> >
> > v9:
> > - Do not report faults from reserved engines (Jianxun)
> >
> > v10:
> > - Remove engine class and instance (Ivan)
> >
> > v11:
> > - Perform kzalloc outside of lock (Auld)
> >
> > v12:
> > - Fix xe_vm_fault_entry kernel docs (Shuicheng)
> >
> > v13:
> > - Rebase and refactor (jcavitt)
> >
> > v14:
> > - Correctly ignore fault mode in save_pagefault_to_vm (jcavitt)
> >
> > Signed-off-by: Jonathan Cavitt <[email protected]>
> > Suggested-by: Matthew Brost <[email protected]>
> > Cc: Shuicheng Lin <[email protected]>
> > Cc: Jianxun Zhang <[email protected]>
> > Cc: Michal Wajdeczko <[email protected]>
> > Cc: Michal Mzorek <[email protected]>
> > Cc: Ivan Briano <[email protected]>
> > Cc: Matthew Auld <[email protected]>
> > ---
> > drivers/gpu/drm/xe/xe_pagefault.c | 26 +++++++++
> > drivers/gpu/drm/xe/xe_vm.c | 88 +++++++++++++++++++++++++++++++
> > drivers/gpu/drm/xe/xe_vm.h | 9 ++++
> > drivers/gpu/drm/xe/xe_vm_types.h | 29 ++++++++++
> > 4 files changed, 152 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/xe/xe_pagefault.c
> > b/drivers/gpu/drm/xe/xe_pagefault.c
> > index 0b625a52a598..5997023a5889 100644
> > --- a/drivers/gpu/drm/xe/xe_pagefault.c
> > +++ b/drivers/gpu/drm/xe/xe_pagefault.c
> > @@ -247,6 +247,31 @@ static void xe_pagefault_print(struct xe_pagefault *pf)
> > pf->consumer.engine_instance);
> > }
> >
> > +static void save_pagefault_to_vm(struct xe_device *xe, struct xe_pagefault
> > *pf)
>
> Every function in xe_pagefault.c starts with 'xe_pagefault_'
>
> So maybe: s/save_pagefault_to_vm/xe_pagefault_save_to_vm
>
> > +{
> > + struct xe_vm *vm;
> > +
> > + /*
> > + * Pagefault may be asociated to VM that is not in fault mode.
> > + * Perform asid_to_vm behavior, except if VM is not in fault
> > + * mode, return VM anyways.
> > + */
> > + down_read(&xe->usm.lock);
> > + vm = xa_load(&xe->usm.asid_to_vm, pf->consumer.asid);
> > + if (vm)
> > + xe_vm_get(vm);
> > + else
> > + vm = ERR_PTR(-EINVAL);
> > + up_read(&xe->usm.lock);
> > +
> > + if (IS_ERR(vm))
> > + return;
> > +
> > + xe_vm_add_fault_entry_pf(vm, pf);
> > +
> > + xe_vm_put(vm);
> > +}
> > +
> > static void xe_pagefault_queue_work(struct work_struct *w)
> > {
> > struct xe_pagefault_queue *pf_queue =
> > @@ -266,6 +291,7 @@ static void xe_pagefault_queue_work(struct work_struct
> > *w)
> > err = xe_pagefault_service(&pf);
> > if (err) {
> > xe_pagefault_print(&pf);
> > + save_pagefault_to_vm(gt_to_xe(pf.gt), &pf);
> > xe_gt_dbg(pf.gt, "Fault response: Unsuccessful %pe\n",
> > ERR_PTR(err));
> > }
> > diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> > index 8ab726289583..e69e10233b00 100644
> > --- a/drivers/gpu/drm/xe/xe_vm.c
> > +++ b/drivers/gpu/drm/xe/xe_vm.c
> > @@ -27,6 +27,7 @@
> > #include "xe_device.h"
> > #include "xe_drm_client.h"
> > #include "xe_exec_queue.h"
> > +#include "xe_gt.h"
> > #include "xe_migrate.h"
> > #include "xe_pat.h"
> > #include "xe_pm.h"
> > @@ -578,6 +579,88 @@ static void preempt_rebind_work_func(struct
> > work_struct *w)
> > trace_xe_vm_rebind_worker_exit(vm);
> > }
> >
> > +static struct xe_hw_engine *
> > +hw_engine_lookup_class_instance(struct xe_vm *vm,
> > + enum xe_engine_class class,
> > + u16 instance)
>
> Can we use xe_hw_engine_lookup or xe_gt_hw_engine rather than adding a
> new helper?
Both of those functions require the GT ID, which is unknown.
>
> > +{
> > + struct xe_device *xe = vm->xe;
> > + struct xe_hw_engine *hwe;
> > + enum xe_hw_engine_id id;
> > + struct xe_gt *gt;
> > + u8 gt_id;
> > +
> > + for_each_gt(gt, xe, gt_id)
> > + for_each_hw_engine(hwe, gt, id)
> > + if (hwe->class == class && hwe->instance == instance)
> > + return hwe;
> > + return NULL;
> > +}
> > +
> > +/**
> > + * xe_vm_add_fault_entry_pf() - Add pagefault to vm fault list
> > + * @vm: The VM.
> > + * @pf: The pagefault.
> > + *
> > + * This function takes the data from the pagefault @pf and saves it to
> > @vm->faults.list.
> > + *
> > + * The function exits silently if the list is full, and reports a warning
> > if the pagefault
> > + * could not be saved to the list.
> > + */
> > +void xe_vm_add_fault_entry_pf(struct xe_vm *vm, struct xe_pagefault *pf)
> > +{
> > + struct xe_vm_fault_entry *e = NULL;
> > + struct xe_hw_engine *hwe;
> > +
> > + /* Do not report faults on reserved engines */
> > + hwe = hw_engine_lookup_class_instance(vm, pf->consumer.engine_class,
> > + pf->consumer.engine_instance);
> > + if (!hwe || xe_hw_engine_is_reserved(hwe))
> > + return;
> > +
> > + e = kzalloc(sizeof(*e), GFP_KERNEL);
> > + if (!e) {
> > + drm_warn(&vm->xe->drm,
> > + "Could not allocate memory for fault!\n");
> > + return;
> > + }
> > +
> > + spin_lock(&vm->faults.lock);
> > +
>
> Michal would say use guard(spinlock)(&vm->faults.lock) here. Probably
> a little cleaner as the goto can be avoided.
>
> > + /*
> > + * Limit the number of faults in the fault list to prevent
> > + * memory overuse.
> > + */
> > + if (vm->faults.len >= MAX_FAULTS_SAVED_PER_VM) {
> > + kfree(e);
> > + goto out;
> > + }
> > +
> > + e->address = pf->consumer.page_addr;
> > + e->address_precision = 1;
> > + e->access_type = pf->consumer.access_type;
> > + e->fault_type = pf->consumer.fault_type;
> > + e->fault_level = pf->consumer.fault_level;
> > +
> > + list_add_tail(&e->list, &vm->faults.list);
> > + vm->faults.len++;
> > +out:
> > + spin_unlock(&vm->faults.lock);
> > +}
> > +
> > +static void xe_vm_clear_fault_entries(struct xe_vm *vm)
> > +{
> > + struct xe_vm_fault_entry *e, *tmp;
> > +
> > + spin_lock(&vm->faults.lock);
>
> Probably a guard here too.
>
> Nits aside, overall LGTM.
>
> Matt
>
> > + list_for_each_entry_safe(e, tmp, &vm->faults.list, list) {
> > + list_del(&e->list);
> > + kfree(e);
> > + }
> > + vm->faults.len = 0;
> > + spin_unlock(&vm->faults.lock);
> > +}
> > +
> > static int xe_vma_ops_alloc(struct xe_vma_ops *vops, bool array_of_binds)
> > {
> > int i;
> > @@ -1503,6 +1586,9 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32
> > flags, struct xe_file *xef)
> > INIT_LIST_HEAD(&vm->userptr.invalidated);
> > spin_lock_init(&vm->userptr.invalidated_lock);
> >
> > + INIT_LIST_HEAD(&vm->faults.list);
> > + spin_lock_init(&vm->faults.lock);
> > +
> > ttm_lru_bulk_move_init(&vm->lru_bulk_move);
> >
> > INIT_WORK(&vm->destroy_work, vm_destroy_work_func);
> > @@ -1808,6 +1894,8 @@ void xe_vm_close_and_put(struct xe_vm *vm)
> > }
> > up_write(&xe->usm.lock);
> >
> > + xe_vm_clear_fault_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 361f10b3c453..e9f2de4189e0 100644
> > --- a/drivers/gpu/drm/xe/xe_vm.h
> > +++ b/drivers/gpu/drm/xe/xe_vm.h
> > @@ -12,6 +12,12 @@
> > #include "xe_map.h"
> > #include "xe_vm_types.h"
> >
> > +/**
> > + * MAX_FAULTS_SAVED_PER_VM - Maximum number of faults each vm can store
> > before future
> > + * faults are discarded to prevent memory overuse
> > + */
> > +#define MAX_FAULTS_SAVED_PER_VM 50
> > +
> > struct drm_device;
> > struct drm_printer;
> > struct drm_file;
> > @@ -22,6 +28,7 @@ struct dma_fence;
> >
> > struct xe_exec_queue;
> > struct xe_file;
> > +struct xe_pagefault;
> > struct xe_sync_entry;
> > struct xe_svm_range;
> > struct drm_exec;
> > @@ -309,6 +316,8 @@ void xe_vm_snapshot_capture_delayed(struct
> > xe_vm_snapshot *snap);
> > void xe_vm_snapshot_print(struct xe_vm_snapshot *snap, struct drm_printer
> > *p);
> > void xe_vm_snapshot_free(struct xe_vm_snapshot *snap);
> >
> > +void xe_vm_add_fault_entry_pf(struct xe_vm *vm, struct xe_pagefault *pf);
> > +
> > /**
> > * xe_vm_set_validating() - Register this task as currently making bos
> > resident
> > * @allow_res_evict: Allow eviction of buffer objects bound to @vm when
> > diff --git a/drivers/gpu/drm/xe/xe_vm_types.h
> > b/drivers/gpu/drm/xe/xe_vm_types.h
> > index 3bf912bfbdcc..fff914fb0aa6 100644
> > --- a/drivers/gpu/drm/xe/xe_vm_types.h
> > +++ b/drivers/gpu/drm/xe/xe_vm_types.h
> > @@ -20,6 +20,7 @@
> > #include "xe_userptr.h"
> >
> > struct xe_bo;
> > +struct xe_pagefault;
> > struct xe_svm_range;
> > struct xe_sync_entry;
> > struct xe_user_fence;
> > @@ -165,6 +166,24 @@ struct xe_userptr_vma {
> >
> > struct xe_device;
> >
> > +/**
> > + * struct xe_vm_fault_entry - Elements of vm->faults.list
> > + * @list: link into @xe_vm.faults.list
> > + * @address: address of the fault
> > + * @address_precision: precision of faulted address
> > + * @access_type: type of address access that resulted in fault
> > + * @fault_type: type of fault reported
> > + * @fault_level: fault level of the fault
> > + */
> > +struct xe_vm_fault_entry {
> > + struct list_head list;
> > + u64 address;
> > + u32 address_precision;
> > + u8 access_type;
> > + u8 fault_type;
> > + u8 fault_level;
> > +};
> > +
> > struct xe_vm {
> > /** @gpuvm: base GPUVM used to track VMAs */
> > struct drm_gpuvm gpuvm;
> > @@ -302,6 +321,16 @@ struct xe_vm {
> > bool capture_once;
> > } error_capture;
> >
> > + /** @faults: List of all faults associated with this VM */
> > + struct {
> > + /** @faults.lock: lock protecting @faults.list */
> > + spinlock_t lock;
> > + /** @faults.list: list of xe_vm_fault_entry entries */
> > + struct list_head list;
> > + /** @faults.len: length of @faults.list */
> > + unsigned int len;
> > + } faults;
> > +
> > /**
> > * @validation: Validation data only valid with the vm resv held.
> > * Note: This is really task state of the task holding the vm resv,
> > --
> > 2.43.0
> >
>
