On Fri, Jun 12, 2026 at 03:53:40PM +0200, Thomas Hellström wrote:
> Add a watch_queue notification channel tied to struct xe_file so that
> userspace can subscribe to asynchronous GPU device events via the
> general kernel notification mechanism.
>
> Introduce DRM_IOCTL_XE_WATCH_QUEUE to let userspace subscribe a
> notification pipe (opened with pipe2(O_NOTIFICATION_PIPE)) to the device
> event stream. Embed the watch_id field (0-255) in the WATCH_INFO_ID
> field of every notification, allowing multiple watches to share a single
> pipe and be told apart by the reader.
>
> Deliver notifications as struct drm_xe_watch_notification records, with
> type always set to WATCH_TYPE_DRM_XE_NOTIFY and subtype drawn from enum
> drm_xe_watch_event. Define DRM_XE_WATCH_EVENT_VM_ERR as the first
> event, posted by the preempt-rebind worker when a VM encounters an
> unrecoverable error. Expose xe_watch_queue_post_vm_err_event() as the
> in-kernel posting API.
>
> Add event definitions in a separate uapi header, <drm/xe_drm_events.h>.
> The main reason is that the header needs to include <linux/watch_queue.h>
> which in turn includes <linux/fcntl.h> which may conflict with the
> system <fcntl.h>. Hence user-space must pay special attention when
> including this file.
>
> Assisted-by: GitHub_Copilot:claude-sonnet-4.6
> Signed-off-by: Thomas Hellström <[email protected]>
> ---
> MAINTAINERS | 1 +
> drivers/gpu/drm/xe/Kconfig | 1 +
> drivers/gpu/drm/xe/Makefile | 1 +
> drivers/gpu/drm/xe/xe_device.c | 7 ++
> drivers/gpu/drm/xe/xe_device_types.h | 6 ++
> drivers/gpu/drm/xe/xe_vm.c | 4 +
> drivers/gpu/drm/xe/xe_vm_types.h | 2 +
> drivers/gpu/drm/xe/xe_watch_queue.c | 111 +++++++++++++++++++++++++++
> drivers/gpu/drm/xe/xe_watch_queue.h | 20 +++++
> include/uapi/drm/xe_drm.h | 45 +++++++++++
> include/uapi/drm/xe_drm_events.h | 62 +++++++++++++++
> 11 files changed, 260 insertions(+)
> create mode 100644 drivers/gpu/drm/xe/xe_watch_queue.c
> create mode 100644 drivers/gpu/drm/xe/xe_watch_queue.h
> create mode 100644 include/uapi/drm/xe_drm_events.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 8c0d9965c636..b7e02cfa692b 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12900,6 +12900,7 @@ F: Documentation/gpu/xe/
> F: drivers/gpu/drm/xe/
> F: include/drm/intel/
> F: include/uapi/drm/xe_drm.h
> +F: include/uapi/drm/xe_drm_events.h
>
> INTEL ELKHART LAKE PSE I/O DRIVER
> M: Raag Jadav <[email protected]>
> diff --git a/drivers/gpu/drm/xe/Kconfig b/drivers/gpu/drm/xe/Kconfig
> index 4d7dcaff2b91..dbdc2fb49c53 100644
> --- a/drivers/gpu/drm/xe/Kconfig
> +++ b/drivers/gpu/drm/xe/Kconfig
> @@ -25,6 +25,7 @@ config DRM_XE
> select DRM_MIPI_DSI
> select RELAY
> select IRQ_WORK
> + select WATCH_QUEUE
> # xe depends on ACPI_VIDEO when ACPI is enabled
> # but for select to work, need to select ACPI_VIDEO's dependencies, ick
> select BACKLIGHT_CLASS_DEVICE if ACPI
> diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
> index 8e7b146880f4..fc8b4023a044 100644
> --- a/drivers/gpu/drm/xe/Makefile
> +++ b/drivers/gpu/drm/xe/Makefile
> @@ -150,6 +150,7 @@ xe-y += xe_bb.o \
> xe_vsec.o \
> xe_wa.o \
> xe_wait_user_fence.o \
> + xe_watch_queue.o \
> xe_wopcm.o
>
> xe-$(CONFIG_I2C) += xe_i2c.o
> diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
> index 867d7c55dc03..788ef2fbd6e5 100644
> --- a/drivers/gpu/drm/xe/xe_device.c
> +++ b/drivers/gpu/drm/xe/xe_device.c
> @@ -9,6 +9,7 @@
> #include <linux/delay.h>
> #include <linux/fault-inject.h>
> #include <linux/units.h>
> +#include <linux/watch_queue.h>
>
> #include <drm/drm_client.h>
> #include <drm/drm_gem_ttm_helper.h>
> @@ -77,6 +78,7 @@
> #include "xe_vsec.h"
> #include "xe_wait_user_fence.h"
> #include "xe_wa.h"
> +#include "xe_watch_queue.h"
>
> #include <generated/xe_device_wa_oob.h>
> #include <generated/xe_wa_oob.h>
> @@ -112,6 +114,8 @@ static int xe_file_open(struct drm_device *dev, struct
> drm_file *file)
> file->driver_priv = xef;
> kref_init(&xef->refcount);
>
> + init_watch_list(&xef->watch_list, NULL);
> +
> task = get_pid_task(rcu_access_pointer(file->pid), PIDTYPE_PID);
> if (task) {
> xef->process_name = kstrdup(task->comm, GFP_KERNEL);
> @@ -126,6 +130,8 @@ static void xe_file_destroy(struct kref *ref)
> {
> struct xe_file *xef = container_of(ref, struct xe_file, refcount);
>
> + remove_watch_from_object(&xef->watch_list, NULL, 0, true);
> +
> xa_destroy(&xef->exec_queue.xa);
> mutex_destroy(&xef->exec_queue.lock);
> xa_destroy(&xef->vm.xa);
> @@ -216,6 +222,7 @@ static const struct drm_ioctl_desc xe_ioctls[] = {
> DRM_IOCTL_DEF_DRV(XE_VM_GET_PROPERTY, xe_vm_get_property_ioctl,
> DRM_RENDER_ALLOW),
> DRM_IOCTL_DEF_DRV(XE_VM_RESTART, xe_vm_restart_ioctl, DRM_RENDER_ALLOW),
> + DRM_IOCTL_DEF_DRV(XE_WATCH_QUEUE, xe_watch_queue_ioctl,
> DRM_RENDER_ALLOW),
> };
>
> static long xe_drm_ioctl(struct file *file, unsigned int cmd, unsigned long
> arg)
> diff --git a/drivers/gpu/drm/xe/xe_device_types.h
> b/drivers/gpu/drm/xe/xe_device_types.h
> index 32dd2ffbc796..ca726ada30a7 100644
> --- a/drivers/gpu/drm/xe/xe_device_types.h
> +++ b/drivers/gpu/drm/xe/xe_device_types.h
> @@ -11,6 +11,7 @@
> #include <drm/drm_device.h>
> #include <drm/drm_file.h>
> #include <drm/ttm/ttm_device.h>
> +#include <linux/watch_queue.h>
>
> #include "xe_devcoredump_types.h"
> #include "xe_drm_ras_types.h"
> @@ -632,6 +633,11 @@ struct xe_file {
>
> /** @refcount: ref count of this xe file */
> struct kref refcount;
> +
> +#ifdef CONFIG_WATCH_QUEUE
> + /** @watch_list: per-file notification source for device events */
> + struct watch_list watch_list;
> +#endif
> };
>
> #endif
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index b69a2e5bd9c9..232de0d948d2 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -13,6 +13,7 @@
> #include <drm/drm_print.h>
> #include <drm/ttm/ttm_tt.h>
> #include <uapi/drm/xe_drm.h>
> +#include <uapi/drm/xe_drm_events.h>
> #include <linux/ascii85.h>
> #include <linux/delay.h>
> #include <linux/kthread.h>
> @@ -45,6 +46,7 @@
> #include "xe_trace_bo.h"
> #include "xe_vm_madvise.h"
> #include "xe_wa.h"
> +#include "xe_watch_queue.h"
>
> #ifdef CONFIG_FAULT_INJECTION
> static DECLARE_FAULT_ATTR(rebind_enospc);
> @@ -584,6 +586,7 @@ static void preempt_rebind_work_func(struct work_struct
> *w)
> }
>
> if (err) {
> + xe_watch_queue_post_vm_err_event(vm->xef, vm->id, err);
> if ((err == -ENOMEM || err == -ENOSPC) &&
> xe_vm_is_restartable(vm)) {
> vm->preempt.rebind_deactivated = true;
> drm_dbg(&vm->xe->drm, "Rebind deactivated VM on error
> %pe\n",
> @@ -2229,6 +2232,7 @@ int xe_vm_create_ioctl(struct drm_device *dev, void
> *data,
> if (err)
> goto err_close_and_put;
>
> + vm->id = id;
> args->vm_id = id;
>
> return 0;
> diff --git a/drivers/gpu/drm/xe/xe_vm_types.h
> b/drivers/gpu/drm/xe/xe_vm_types.h
> index 7d295c3b8456..19a673099588 100644
> --- a/drivers/gpu/drm/xe/xe_vm_types.h
> +++ b/drivers/gpu/drm/xe/xe_vm_types.h
> @@ -407,6 +407,8 @@ struct xe_vm {
> bool batch_invalidate_tlb;
> /** @xef: Xe file handle for tracking this VM's drm client */
> struct xe_file *xef;
> + /** @id: The id of the VM in the VM table of @xef. */
> + u32 id;
> };
>
> /** struct xe_vma_op_map - VMA map operation */
> diff --git a/drivers/gpu/drm/xe/xe_watch_queue.c
> b/drivers/gpu/drm/xe/xe_watch_queue.c
> new file mode 100644
> index 000000000000..32763591075b
> --- /dev/null
> +++ b/drivers/gpu/drm/xe/xe_watch_queue.c
> @@ -0,0 +1,111 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2026 Intel Corporation
> + */
> +
> +#include <linux/slab.h>
> +#include <linux/timekeeping.h>
> +#include <linux/watch_queue.h>
> +
> +#include <uapi/drm/xe_drm.h>
> +#include <uapi/drm/xe_drm_events.h>
> +
> +#include "xe_device.h"
> +#include "xe_device_types.h"
> +#include "xe_macros.h"
> +#include "xe_watch_queue.h"
> +
> +/**
> + * struct xe_watch_notification_vm_err - kernel-side VM error event
> notification
> + * @base: common watch notification header; type is
> %WATCH_TYPE_DRM_XE_NOTIFY,
> + * subtype is %DRM_XE_WATCH_EVENT_VM_ERR
> + * @vm_id: ID of the VM that hit error
> + * @error_code: error code describing the error condition (negative errno)
> + * @timestamp_ns: CLOCK_MONOTONIC timestamp in nanoseconds at the point the
> + * error was detected
> + *
> + * Layout mirrors &struct drm_xe_watch_notification_vm_err.
> + */
> +struct xe_watch_notification_vm_err {
> + struct watch_notification base;
> + u32 vm_id;
> + s32 error_code;
> + u64 timestamp_ns;
> +};
> +
> +/**
> + * xe_watch_queue_ioctl() - Subscribe a pipe to per-file device event
> notifications
> + * @dev: DRM device
> + * @data: pointer to &struct drm_xe_watch_queue from userspace
> + * @file: DRM file handle of the subscribing process
> + *
> + * Subscribes a notification pipe to receive Xe device events for the calling
> + * process's file handle. Only events scoped to this file (e.g. VM error on
> a
> + * VM owned by this file) are delivered. The pipe must have been opened with
> + * O_NOTIFICATION_PIPE and sized with %IOC_WATCH_QUEUE_SET_SIZE before
> calling
> + * this IOCTL.
> + *
> + * Return: 0 on success, negative errno on failure.
> + */
> +int xe_watch_queue_ioctl(struct drm_device *dev, void *data, struct drm_file
> *file)
> +{
> + struct xe_file *xef = file->driver_priv;
> + struct xe_device *xe = to_xe_device(dev);
> + struct drm_xe_watch_queue *args = data;
> + struct watch_queue *wqueue;
> + struct watch *watch;
> + int ret;
> +
> + if (XE_IOCTL_DBG(xe, args->flags || args->pad))
> + return -EINVAL;
> + if (XE_IOCTL_DBG(xe, args->watch_id > 0xff))
> + return -EINVAL;
> +
> + wqueue = get_watch_queue(args->fd);
> + if (XE_IOCTL_DBG(xe, IS_ERR(wqueue)))
> + return PTR_ERR(wqueue);
> +
> + watch = kzalloc_obj(*watch, GFP_KERNEL | __GFP_ACCOUNT);
> + if (XE_IOCTL_DBG(xe, !watch)) {
> + ret = -ENOMEM;
> + goto out_put_queue;
> + }
> +
> + init_watch(watch, wqueue);
> + watch->id = 0;
> + watch->info_id = (u32)args->watch_id << WATCH_INFO_ID__SHIFT;
> +
> + ret = add_watch_to_object(watch, &xef->watch_list);
> + if (XE_IOCTL_DBG(xe, ret))
> + kfree(watch);
> +
> +out_put_queue:
> + put_watch_queue(wqueue);
> + return ret;
> +}
> +
> +/**
> + * xe_watch_queue_post_vm_err_event() - Post a VM error event
> + * @xef: xe file handle that owns the VM
> + * @vm_id: userspace ID of the VM that hit error
> + * @error_code: error code describing the error condition (negative errno)
> + *
> + * Posts a %DRM_XE_WATCH_EVENT_VM_ERR notification carrying @vm_id and
> + * @error_code to every pipe that @xef has subscribed via
> + * %DRM_IOCTL_XE_WATCH_QUEUE. Only the owning process is notified,
> + * preventing information leaks to other clients.
> + */
> +void xe_watch_queue_post_vm_err_event(struct xe_file *xef, u32 vm_id,
> + int error_code)
> +{
> + struct xe_watch_notification_vm_err n = {};
> +
> + n.base.type = WATCH_TYPE_DRM_XE_NOTIFY;
> + n.base.subtype = DRM_XE_WATCH_EVENT_VM_ERR;
> + n.base.info = watch_sizeof(struct xe_watch_notification_vm_err);
> + n.vm_id = vm_id;
> + n.error_code = error_code;
> + n.timestamp_ns = ktime_get_ns();
> +
> + post_watch_notification(&xef->watch_list, &n.base, current_cred(), 0);
Is this reclaim safe (i.e., could we post a watch notification in direct
reclaim from our shrinker)? From my look, I think the answer is yes. I
ask because whatever we land here, I think the answer must be KMD->UMD
events are reclaim safe.
Matt
> +}
> diff --git a/drivers/gpu/drm/xe/xe_watch_queue.h
> b/drivers/gpu/drm/xe/xe_watch_queue.h
> new file mode 100644
> index 000000000000..ad199ee68205
> --- /dev/null
> +++ b/drivers/gpu/drm/xe/xe_watch_queue.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright © 2026 Intel Corporation
> + */
> +
> +#ifndef _XE_WATCH_QUEUE_H_
> +#define _XE_WATCH_QUEUE_H_
> +
> +#include <linux/types.h>
> +
> +struct drm_device;
> +struct drm_file;
> +struct xe_file;
> +
> +int xe_watch_queue_ioctl(struct drm_device *dev, void *data,
> + struct drm_file *file);
> +void xe_watch_queue_post_vm_err_event(struct xe_file *xef, u32 vm_id,
> + int error_code);
> +
> +#endif /* _XE_WATCH_QUEUE_H_ */
> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
> index 8d5e3f06b8d4..0083dd712f7e 100644
> --- a/include/uapi/drm/xe_drm.h
> +++ b/include/uapi/drm/xe_drm.h
> @@ -86,6 +86,7 @@ extern "C" {
> * - &DRM_IOCTL_XE_EXEC_QUEUE_SET_PROPERTY
> * - &DRM_IOCTL_XE_VM_GET_PROPERTY
> * - &DRM_IOCTL_XE_VM_RESTART
> + * - &DRM_IOCTL_XE_WATCH_QUEUE
> */
>
> /*
> @@ -112,6 +113,7 @@ extern "C" {
> #define DRM_XE_EXEC_QUEUE_SET_PROPERTY 0x0e
> #define DRM_XE_VM_GET_PROPERTY 0x0f
> #define DRM_XE_VM_RESTART 0x10
> +#define DRM_XE_WATCH_QUEUE 0x11
>
> /* Must be kept compact -- no holes */
>
> @@ -132,6 +134,7 @@ extern "C" {
> #define DRM_IOCTL_XE_EXEC_QUEUE_SET_PROPERTY DRM_IOW(DRM_COMMAND_BASE +
> DRM_XE_EXEC_QUEUE_SET_PROPERTY, struct drm_xe_exec_queue_set_property)
> #define DRM_IOCTL_XE_VM_GET_PROPERTY DRM_IOWR(DRM_COMMAND_BASE +
> DRM_XE_VM_GET_PROPERTY, struct drm_xe_vm_get_property)
> #define DRM_IOCTL_XE_VM_RESTART
> DRM_IOW(DRM_COMMAND_BASE + DRM_XE_VM_RESTART, struct drm_xe_vm_restart)
> +#define DRM_IOCTL_XE_WATCH_QUEUE DRM_IOW(DRM_COMMAND_BASE +
> DRM_XE_WATCH_QUEUE, struct drm_xe_watch_queue)
>
> /**
> * DOC: Xe IOCTL Extensions
> @@ -2653,6 +2656,48 @@ enum drm_xe_ras_error_component {
> [DRM_XE_RAS_ERR_COMP_SOC_INTERNAL] = "soc-internal" \
> }
>
> +/**
> + * DOC: DRM_XE_WATCH_QUEUE
> + *
> + * Subscribe a notification pipe to receive device events for the calling
> + * process's DRM file handle. Events are scoped to the subscribing file:
> + * only events that belong to that file (for example, VM error on a VM
> created
> + * through the same file) are delivered, preventing information leaks between
> + * processes sharing the same GPU device.
> + *
> + * The pipe must first be opened with O_NOTIFICATION_PIPE (i.e. O_EXCL passed
> + * to pipe2()) and sized via %IOC_WATCH_QUEUE_SET_SIZE before subscribing.
> + *
> + * Events are delivered as notification records read from the pipe. The
> + * @watch_id field is embedded in the notification info field and can be used
> + * to distinguish multiple watches sharing a pipe.
> + *
> + * Currently defined event subtypes:
> + * - %DRM_XE_WATCH_EVENT_VM_ERR - a VM owned by this file has encountered
> an error
> + */
> +
> +/**
> + * struct drm_xe_watch_queue - subscribe to device event notifications
> + *
> + * Used with %DRM_IOCTL_XE_WATCH_QUEUE. Notifications are scoped to the
> + * DRM file handle used to issue this IOCTL.
> + */
> +struct drm_xe_watch_queue {
> + /** @fd: file descriptor of pipe opened with O_NOTIFICATION_PIPE */
> + __u32 fd;
> +
> + /**
> + * @watch_id: identifier (0–255) embedded in the watch notification
> + * info field; allows multiplexing several watches on one pipe
> + */
> + __u32 watch_id;
> +
> + /** @flags: must be zero */
> + __u32 flags;
> +
> + /** @pad: reserved, must be zero */
> + __u32 pad;
> +};
> #if defined(__cplusplus)
> }
> #endif
> diff --git a/include/uapi/drm/xe_drm_events.h
> b/include/uapi/drm/xe_drm_events.h
> new file mode 100644
> index 000000000000..6cc7528bfb9b
> --- /dev/null
> +++ b/include/uapi/drm/xe_drm_events.h
> @@ -0,0 +1,62 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright © 2026 Intel Corporation
> + */
> +
> +#ifndef _UAPI_XE_DRM_EVENTS_H_
> +#define _UAPI_XE_DRM_EVENTS_H_
> +
> +#include <linux/types.h>
> +#include <linux/watch_queue.h>
> +
> +#if defined(__cplusplus)
> +extern "C" {
> +#endif
> +
> +/**
> + * enum drm_xe_watch_event - Xe device watch event subtypes
> + *
> + * Subtypes for notifications delivered via %WATCH_TYPE_DRM_XE_NOTIFY when
> + * reading from a pipe subscribed with %DRM_IOCTL_XE_WATCH_QUEUE.
> + */
> +enum drm_xe_watch_event {
> + /**
> + * @DRM_XE_WATCH_EVENT_VM_ERR: a VM has encountered an error.
> + *
> + * Indicates that a fatal or resource error occurred within the given
> + * VM. The vm_id of the affected VM is carried in the
> + * @drm_xe_watch_notification_vm_err::vm_id field of the extended
> + * notification record.
> + */
> + DRM_XE_WATCH_EVENT_VM_ERR = 0,
> +};
> +
> +/**
> + * struct drm_xe_watch_notification_vm_err - VM error event notification
> + *
> + * Notification record delivered for %DRM_XE_WATCH_EVENT_VM_ERR.
> + * The record type is always %WATCH_TYPE_DRM_XE_NOTIFY and the subtype is
> + * %DRM_XE_WATCH_EVENT_VM_ERR.
> + */
> +struct drm_xe_watch_notification_vm_err {
> + /** @base: common watch notification header */
> + struct watch_notification base;
> +
> + /** @vm_id: ID of the VM that encountered an error */
> + __u32 vm_id;
> +
> + /** @error_code: error code describing the error condition (negative
> errno) */
> + __s32 error_code;
> +
> + /**
> + * @timestamp_ns: CLOCK_MONOTONIC timestamp in nanoseconds at the
> + * point the error was detected
> + */
> + __u64 timestamp_ns;
> +};
> +
> +#if defined(__cplusplus)
> +}
> +#endif
> +
> +#endif /* _UAPI_XE_DRM_EVENTS_H_ */
> --
> 2.54.0
>
