Re: [PATCH 07/26] drm/xe/pf: Add support for encap/decap of bitstream to/from packet

[Michal Wajdeczko <michal.wajdeczko@intel.com>]

On 10/11/2025 9:38 PM, Michał Winiarski wrote:
> Add debugfs handlers for migration state and handle bitstream
> .read()/.write() to convert from bitstream to/from migration data
> packets.
> As descriptor/trailer are handled at this layer - add handling for both
> save and restore side.
> 
> Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_gt_sriov_pf_control.c   |  18 +
>  drivers/gpu/drm/xe/xe_gt_sriov_pf_control.h   |   1 +
>  drivers/gpu/drm/xe/xe_sriov_pf.c              |   1 +
>  drivers/gpu/drm/xe/xe_sriov_pf_control.c      |   5 +
>  drivers/gpu/drm/xe/xe_sriov_pf_debugfs.c      |  45 +++
>  drivers/gpu/drm/xe/xe_sriov_pf_migration.c    |  56 +++
>  .../gpu/drm/xe/xe_sriov_pf_migration_data.c   | 353 ++++++++++++++++++
>  .../gpu/drm/xe/xe_sriov_pf_migration_data.h   |   5 +
>  .../gpu/drm/xe/xe_sriov_pf_migration_types.h  |   9 +
>  9 files changed, 493 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_control.c b/drivers/gpu/drm/xe/xe_gt_sriov_pf_control.c
> index 04a4e92133c2e..092d3d710bca1 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_control.c
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_control.c
> @@ -814,6 +814,23 @@ bool xe_gt_sriov_pf_control_check_vf_data_wip(struct xe_gt *gt, unsigned int vfi
>  	return pf_check_vf_state(gt, vfid, XE_GT_SRIOV_STATE_MIGRATION_DATA_WIP);
>  }
>  
> +/**
> + * xe_gt_sriov_pf_control_vf_data_eof() - indicate the end of SR-IOV VF migration data production
> + * @gt: the &struct xe_gt
> + * @vfid: the VF identifier
> + *
> + * This function is for PF only.
> + */
> +void xe_gt_sriov_pf_control_vf_data_eof(struct xe_gt *gt, unsigned int vfid)
> +{
> +	struct wait_queue_head *wq = xe_sriov_pf_migration_waitqueue(gt_to_xe(gt), vfid);
> +
> +	if (!pf_exit_vf_state(gt, vfid, XE_GT_SRIOV_STATE_MIGRATION_DATA_WIP))
> +		pf_enter_vf_state_machine_bug(gt, vfid);
> +
> +	wake_up_all(wq);
> +}
> +
>  static void pf_exit_vf_save_wip(struct xe_gt *gt, unsigned int vfid)
>  {
>  	pf_exit_vf_state(gt, vfid, XE_GT_SRIOV_STATE_SAVE_WIP);
> @@ -840,6 +857,7 @@ static bool pf_handle_vf_save_wip(struct xe_gt *gt, unsigned int vfid)
>  	if (!pf_check_vf_state(gt, vfid, XE_GT_SRIOV_STATE_SAVE_WIP))
>  		return false;
>  
> +	xe_gt_sriov_pf_control_vf_data_eof(gt, vfid);

above call can lead to state_machine_bug but here you just continue as nothing happen and moving to SAVED state

maybe that logic of that function should moved to a helper that at least returns bool so you can make the right decision?

>  	pf_exit_vf_save_wip(gt, vfid);
>  	pf_enter_vf_saved(gt, vfid);
>  
> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_control.h b/drivers/gpu/drm/xe/xe_gt_sriov_pf_control.h
> index 2e121e8132dcf..caf20dd063b1b 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_control.h
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_control.h
> @@ -15,6 +15,7 @@ int xe_gt_sriov_pf_control_init(struct xe_gt *gt);
>  void xe_gt_sriov_pf_control_restart(struct xe_gt *gt);
>  
>  bool xe_gt_sriov_pf_control_check_vf_data_wip(struct xe_gt *gt, unsigned int vfid);
> +void xe_gt_sriov_pf_control_vf_data_eof(struct xe_gt *gt, unsigned int vfid);
>  
>  int xe_gt_sriov_pf_control_pause_vf(struct xe_gt *gt, unsigned int vfid);
>  int xe_gt_sriov_pf_control_resume_vf(struct xe_gt *gt, unsigned int vfid);
> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf.c b/drivers/gpu/drm/xe/xe_sriov_pf.c
> index 95743c7af8050..5d115627f3f2f 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf.c
> @@ -16,6 +16,7 @@
>  #include "xe_sriov_pf.h"
>  #include "xe_sriov_pf_helpers.h"
>  #include "xe_sriov_pf_migration.h"
> +#include "xe_sriov_pf_migration_data.h"
>  #include "xe_sriov_pf_service.h"
>  #include "xe_sriov_printk.h"
>  
> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_control.c b/drivers/gpu/drm/xe/xe_sriov_pf_control.c
> index e64c7b56172c6..10e1f18aa8b11 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf_control.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf_control.c
> @@ -6,6 +6,7 @@
>  #include "xe_device.h"
>  #include "xe_gt_sriov_pf_control.h"
>  #include "xe_sriov_pf_control.h"
> +#include "xe_sriov_pf_migration_data.h"
>  #include "xe_sriov_printk.h"
>  
>  /**
> @@ -165,6 +166,10 @@ int xe_sriov_pf_control_save_vf(struct xe_device *xe, unsigned int vfid)
>  	unsigned int id;
>  	int ret;
>  
> +	ret = xe_sriov_pf_migration_data_save_init(xe, vfid);
> +	if (ret)
> +		return ret;
> +
>  	for_each_gt(gt, xe, id) {
>  		ret = xe_gt_sriov_pf_control_save_vf(gt, vfid);
>  		if (ret)
> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_debugfs.c b/drivers/gpu/drm/xe/xe_sriov_pf_debugfs.c
> index 74eeabef91c57..ce780719760a6 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf_debugfs.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf_debugfs.c
> @@ -13,6 +13,7 @@
>  #include "xe_sriov_pf_control.h"
>  #include "xe_sriov_pf_debugfs.h"
>  #include "xe_sriov_pf_helpers.h"
> +#include "xe_sriov_pf_migration_data.h"
>  #include "xe_sriov_pf_service.h"
>  #include "xe_sriov_printk.h"
>  #include "xe_tile_sriov_pf_debugfs.h"
> @@ -71,6 +72,7 @@ static void pf_populate_pf(struct xe_device *xe, struct dentry *pfdent)
>   *      /sys/kernel/debug/dri/BDF/
>   *      ├── sriov
>   *      │   ├── vf1
> + *      │   │   ├── migration_data
>   *      │   │   ├── pause
>   *      │   │   ├── reset
>   *      │   │   ├── resume
> @@ -159,6 +161,48 @@ DEFINE_VF_CONTROL_ATTRIBUTE(reset_vf);
>  DEFINE_VF_RW_CONTROL_ATTRIBUTE(save_vf);
>  DEFINE_VF_RW_CONTROL_ATTRIBUTE(restore_vf);
>  
> +static ssize_t data_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
> +{
> +	struct dentry *dent = file_dentry(file);
> +	struct dentry *vfdentry = dent->d_parent;
> +	struct dentry *migration_dentry = vfdentry->d_parent;
> +	unsigned int vfid = (uintptr_t)vfdentry->d_inode->i_private;
> +	struct xe_device *xe = migration_dentry->d_inode->i_private;

we have extract_xe() / extract_vfid() helpers for that

> +
> +	xe_assert(xe, vfid);
> +	xe_sriov_pf_assert_vfid(xe, vfid);
> +
> +	if (*pos)
> +		return -ESPIPE;
> +
> +	return xe_sriov_pf_migration_data_write(xe, vfid, buf, count);
> +}
> +
> +static ssize_t data_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> +{
> +	struct dentry *dent = file_dentry(file);
> +	struct dentry *vfdentry = dent->d_parent;
> +	struct dentry *migration_dentry = vfdentry->d_parent;
> +	unsigned int vfid = (uintptr_t)vfdentry->d_inode->i_private;
> +	struct xe_device *xe = migration_dentry->d_inode->i_private;
> +
> +	xe_assert(xe, vfid);
> +	xe_sriov_pf_assert_vfid(xe, vfid);
> +
> +	if (*ppos)
> +		return -ESPIPE;
> +
> +	return xe_sriov_pf_migration_data_read(xe, vfid, buf, count);
> +}
> +
> +static const struct file_operations data_vf_fops = {
> +	.owner		= THIS_MODULE,
> +	.open		= simple_open,
> +	.write		= data_write,
> +	.read		= data_read,
> +	.llseek		= default_llseek,
> +};
> +
>  static void pf_populate_vf(struct xe_device *xe, struct dentry *vfdent)
>  {
>  	debugfs_create_file("pause", 0200, vfdent, xe, &pause_vf_fops);
> @@ -167,6 +211,7 @@ static void pf_populate_vf(struct xe_device *xe, struct dentry *vfdent)
>  	debugfs_create_file("reset", 0200, vfdent, xe, &reset_vf_fops);
>  	debugfs_create_file("save", 0600, vfdent, xe, &save_vf_fops);
>  	debugfs_create_file("restore", 0600, vfdent, xe, &restore_vf_fops);
> +	debugfs_create_file("migration_data", 0600, vfdent, xe, &data_vf_fops);
>  }
>  
>  static void pf_populate_with_tiles(struct xe_device *xe, struct dentry *dent, unsigned int vfid)
> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_migration.c b/drivers/gpu/drm/xe/xe_sriov_pf_migration.c
> index d39cee66589b5..9cc178126cbdc 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf_migration.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf_migration.c
> @@ -56,6 +56,18 @@ static bool pf_check_migration_support(struct xe_device *xe)
>  	return IS_ENABLED(CONFIG_DRM_XE_DEBUG);
>  }
>  
> +static void pf_migration_cleanup(struct drm_device *dev, void *arg)
> +{
> +	struct xe_sriov_pf_migration *migration = arg;
> +
> +	if (!IS_ERR_OR_NULL(migration->pending))
> +		xe_sriov_pf_migration_data_free(migration->pending);
> +	if (!IS_ERR_OR_NULL(migration->trailer))
> +		xe_sriov_pf_migration_data_free(migration->trailer);
> +	if (!IS_ERR_OR_NULL(migration->descriptor))
> +		xe_sriov_pf_migration_data_free(migration->descriptor);

maybe instead of checking IS_ERR_OR_NULL here, move the check to data_free() ?

> +}
> +
>  /**
>   * xe_sriov_pf_migration_init() - Initialize support for SR-IOV VF migration.
>   * @xe: the &struct xe_device
> @@ -65,6 +77,7 @@ static bool pf_check_migration_support(struct xe_device *xe)
>  int xe_sriov_pf_migration_init(struct xe_device *xe)
>  {
>  	unsigned int n, totalvfs;
> +	int err;
>  
>  	xe_assert(xe, IS_SRIOV_PF(xe));
>  
> @@ -76,7 +89,15 @@ int xe_sriov_pf_migration_init(struct xe_device *xe)
>  	for (n = 1; n <= totalvfs; n++) {
>  		struct xe_sriov_pf_migration *migration = pf_pick_migration(xe, n);
>  
> +		err = drmm_mutex_init(&xe->drm, &migration->lock);
> +		if (err)
> +			return err;
> +
>  		init_waitqueue_head(&migration->wq);
> +
> +		err = drmm_add_action_or_reset(&xe->drm, pf_migration_cleanup, migration);
> +		if (err)
> +			return err;
>  	}
>  
>  	return 0;
> @@ -162,6 +183,36 @@ xe_sriov_pf_migration_consume(struct xe_device *xe, unsigned int vfid)
>  	return data;
>  }
>  
> +static int pf_handle_descriptor(struct xe_device *xe, unsigned int vfid,
> +				struct xe_sriov_pf_migration_data *data)
> +{
> +	if (data->tile != 0 || data->gt != 0)
> +		return -EINVAL;
> +
> +	xe_sriov_pf_migration_data_free(data);
> +
> +	return 0;
> +}
> +
> +static int pf_handle_trailer(struct xe_device *xe, unsigned int vfid,
> +			     struct xe_sriov_pf_migration_data *data)
> +{
> +	struct xe_gt *gt;
> +	u8 gt_id;
> +
> +	if (data->tile != 0 || data->gt != 0)
> +		return -EINVAL;
> +	if (data->offset != 0 || data->size != 0 || data->buff || data->bo)
> +		return -EINVAL;

who will free the data packet if we return errors here?

> +
> +	xe_sriov_pf_migration_data_free(data);
> +
> +	for_each_gt(gt, xe, gt_id)
> +		xe_gt_sriov_pf_control_vf_data_eof(gt, vfid);
> +
> +	return 0;
> +}
> +
>  /**
>   * xe_sriov_pf_migration_produce() - Produce a SR-IOV VF migration data packet for device to process
>   * @xe: the &struct xe_device
> @@ -180,6 +231,11 @@ int xe_sriov_pf_migration_produce(struct xe_device *xe, unsigned int vfid,
>  	if (!IS_SRIOV_PF(xe))
>  		return -ENODEV;
>  
> +	if (data->type == XE_SRIOV_MIG_DATA_DESCRIPTOR)
> +		return pf_handle_descriptor(xe, vfid, data);
> +	else if (data->type == XE_SRIOV_MIG_DATA_TRAILER)
> +		return pf_handle_trailer(xe, vfid, data);
> +
>  	gt = xe_device_get_gt(xe, data->gt);
>  	if (!gt || data->tile != gt->tile->id) {
>  		xe_sriov_err_ratelimited(xe, "VF%d Unknown GT - tile_id:%d, gt_id:%d\n",
> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_migration_data.c b/drivers/gpu/drm/xe/xe_sriov_pf_migration_data.c
> index cfc6b512c6674..9a2777dcf9a6b 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf_migration_data.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf_migration_data.c
> @@ -5,7 +5,45 @@
>  
>  #include "xe_bo.h"
>  #include "xe_device.h"
> +#include "xe_sriov_pf_helpers.h"
> +#include "xe_sriov_pf_migration.h"
>  #include "xe_sriov_pf_migration_data.h"
> +#include "xe_sriov_printk.h"
> +
> +static struct mutex *pf_migration_mutex(struct xe_device *xe, unsigned int vfid)
> +{
> +	xe_assert(xe, IS_SRIOV_PF(xe));
> +	xe_assert(xe, vfid <= xe_sriov_pf_get_totalvfs(xe));
> +	return &xe->sriov.pf.vfs[vfid].migration.lock;
> +}
> +
> +static struct xe_sriov_pf_migration_data **pf_pick_pending(struct xe_device *xe, unsigned int vfid)
> +{
> +	xe_assert(xe, IS_SRIOV_PF(xe));
> +	xe_assert(xe, vfid <= xe_sriov_pf_get_totalvfs(xe));
> +	lockdep_assert_held(pf_migration_mutex(xe, vfid));
> +
> +	return &xe->sriov.pf.vfs[vfid].migration.pending;
> +}
> +
> +static struct xe_sriov_pf_migration_data **
> +pf_pick_descriptor(struct xe_device *xe, unsigned int vfid)
> +{
> +	xe_assert(xe, IS_SRIOV_PF(xe));
> +	xe_assert(xe, vfid <= xe_sriov_pf_get_totalvfs(xe));
> +	lockdep_assert_held(pf_migration_mutex(xe, vfid));
> +
> +	return &xe->sriov.pf.vfs[vfid].migration.descriptor;
> +}
> +
> +static struct xe_sriov_pf_migration_data **pf_pick_trailer(struct xe_device *xe, unsigned int vfid)
> +{
> +	xe_assert(xe, IS_SRIOV_PF(xe));
> +	xe_assert(xe, vfid <= xe_sriov_pf_get_totalvfs(xe));
> +	lockdep_assert_held(pf_migration_mutex(xe, vfid));
> +
> +	return &xe->sriov.pf.vfs[vfid].migration.trailer;
> +}
>  
>  static bool data_needs_bo(struct xe_sriov_pf_migration_data *data)
>  {
> @@ -133,3 +171,318 @@ int xe_sriov_pf_migration_data_init_from_hdr(struct xe_sriov_pf_migration_data *
>  
>  	return mig_data_init(data);
>  }
> +
> +static ssize_t vf_mig_data_hdr_read(struct xe_sriov_pf_migration_data *data,
> +				    char __user *buf, size_t len)
> +{
> +	loff_t offset = sizeof(data->hdr) - data->hdr_remaining;
> +
> +	if (!data->hdr_remaining)
> +		return -EINVAL;
> +
> +	if (len > data->hdr_remaining)
> +		len = data->hdr_remaining;
> +
> +	if (copy_to_user(buf, (void *)&data->hdr + offset, len))
> +		return -EFAULT;
> +
> +	data->hdr_remaining -= len;
> +
> +	return len;
> +}
> +
> +static ssize_t vf_mig_data_read(struct xe_sriov_pf_migration_data *data,
> +				char __user *buf, size_t len)
> +{
> +	if (len > data->remaining)
> +		len = data->remaining;
> +
> +	if (copy_to_user(buf, data->vaddr + (data->size - data->remaining), len))
> +		return -EFAULT;
> +
> +	data->remaining -= len;
> +
> +	return len;
> +}
> +
> +static ssize_t __vf_mig_data_read_single(struct xe_sriov_pf_migration_data **data,
> +					 unsigned int vfid, char __user *buf, size_t len)
> +{
> +	ssize_t copied = 0;
> +
> +	if ((*data)->hdr_remaining)
> +		copied = vf_mig_data_hdr_read(*data, buf, len);
> +	else
> +		copied = vf_mig_data_read(*data, buf, len);
> +
> +	if ((*data)->remaining == 0 && (*data)->hdr_remaining == 0) {
> +		xe_sriov_pf_migration_data_free(*data);
> +		*data = NULL;
> +	}
> +
> +	return copied;
> +}
> +
> +static struct xe_sriov_pf_migration_data **vf_mig_pick_data(struct xe_device *xe, unsigned int vfid)
> +{
> +	struct xe_sriov_pf_migration_data **data;
> +
> +	data = pf_pick_descriptor(xe, vfid);
> +	if (*data)
> +		return data;
> +
> +	data = pf_pick_pending(xe, vfid);
> +	if (*data == NULL)
> +		*data = xe_sriov_pf_migration_consume(xe, vfid);
> +	if (!IS_ERR_OR_NULL(*data))
> +		return data;
> +	else if (IS_ERR(*data) && PTR_ERR(*data) != -ENODATA)
> +		return data;
> +
> +	data = pf_pick_trailer(xe, vfid);
> +	if (*data)
> +		return data;
> +
> +	return ERR_PTR(-ENODATA);
> +}
> +
> +static ssize_t vf_mig_data_read_single(struct xe_device *xe, unsigned int vfid,
> +				       char __user *buf, size_t len)
> +{
> +	struct xe_sriov_pf_migration_data **data = vf_mig_pick_data(xe, vfid);
> +
> +	if (IS_ERR_OR_NULL(data))
> +		return PTR_ERR(data);
> +
> +	return __vf_mig_data_read_single(data, vfid, buf, len);
> +}
> +
> +/**
> + * xe_sriov_pf_migration_data_read() - Read migration data from the device
> + * @gt: the &struct xe_device

@xe

> + * @vfid: the VF identifier
> + * @buf: start address of userspace buffer
> + * @len: requested read size from userspace
> + *
> + * Return: number of bytes that has been successfully read
> + *	   0 if no more migration data is available
> + *	   -errno on failure

you likely need to add some punctuation here to properly render the doc

> + */
> +ssize_t xe_sriov_pf_migration_data_read(struct xe_device *xe, unsigned int vfid,
> +					char __user *buf, size_t len)
> +{
> +	ssize_t ret, consumed = 0;
> +
> +	xe_assert(xe, IS_SRIOV_PF(xe));
> +
> +	ret = mutex_lock_interruptible(pf_migration_mutex(xe, vfid));
> +	if (ret)
> +		return ret;
> +
> +	while (consumed < len) {
> +		ret = vf_mig_data_read_single(xe, vfid, buf, len - consumed);
> +		if (ret == -ENODATA)
> +			goto out;
> +		if (ret < 0) {
> +			mutex_unlock(pf_migration_mutex(xe, vfid));
> +			return ret;
> +		}
> +
> +		consumed += ret;
> +		buf += ret;
> +	}
> +
> +out:
> +	mutex_unlock(pf_migration_mutex(xe, vfid));
> +	return consumed;
> +}
> +
> +static ssize_t vf_mig_hdr_write(struct xe_sriov_pf_migration_data *data,
> +				const char __user *buf, size_t len)
> +{
> +	loff_t offset = sizeof(data->hdr) - data->hdr_remaining;
> +	int ret;
> +
> +	if (WARN_ON(!data->hdr_remaining))

xe_WARN_ON(xe, ... ) if having full WARN is really important

> +		return -EINVAL;
> +
> +	if (len > data->hdr_remaining)
> +		len = data->hdr_remaining;
> +
> +	if (copy_from_user((void *)&data->hdr + offset, buf, len))
> +		return -EFAULT;
> +
> +	data->hdr_remaining -= len;
> +
> +	if (!data->hdr_remaining) {
> +		ret = xe_sriov_pf_migration_data_init_from_hdr(data);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return len;
> +}
> +
> +static ssize_t vf_mig_data_write(struct xe_sriov_pf_migration_data *data,
> +				 const char __user *buf, size_t len)
> +{
> +	if (len > data->remaining)
> +		len = data->remaining;
> +
> +	if (copy_from_user(data->vaddr + (data->size - data->remaining), buf, len))
> +		return -EFAULT;
> +
> +	data->remaining -= len;
> +
> +	return len;
> +}
> +
> +static ssize_t vf_mig_data_write_single(struct xe_device *xe, unsigned int vfid,
> +					const char __user *buf, size_t len)
> +{
> +	struct xe_sriov_pf_migration_data **data = pf_pick_pending(xe, vfid);
> +	int ret;
> +	ssize_t copied;
> +
> +	if (IS_ERR_OR_NULL(*data)) {
> +		*data = xe_sriov_pf_migration_data_alloc(xe);
> +		if (*data == NULL)
> +			return -ENOMEM;
> +	}
> +
> +	if ((*data)->hdr_remaining)
> +		copied = vf_mig_hdr_write(*data, buf, len);
> +	else
> +		copied = vf_mig_data_write(*data, buf, len);
> +
> +	if ((*data)->hdr_remaining == 0 && (*data)->remaining == 0) {
> +		ret = xe_sriov_pf_migration_produce(xe, vfid, *data);
> +		if (ret) {
> +			xe_sriov_pf_migration_data_free(*data);
> +			return ret;
> +		}
> +
> +		*data = NULL;
> +	}
> +
> +	return copied;
> +}
> +
> +/**
> + * xe_sriov_pf_migration_data_write() - Write migration data to the device
> + * @gt: the &struct xe_device

@xe

> + * @vfid: the VF identifier
> + * @buf: start address of userspace buffer
> + * @len: requested write size from userspace
> + *
> + * Return: number of bytes that has been successfully written
> + *	   -errno on failure
> + */
> +ssize_t xe_sriov_pf_migration_data_write(struct xe_device *xe, unsigned int vfid,
> +					 const char __user *buf, size_t len)
> +{
> +	ssize_t ret, produced = 0;
> +
> +	xe_assert(xe, IS_SRIOV_PF(xe));
> +
> +	ret = mutex_lock_interruptible(pf_migration_mutex(xe, vfid));
> +	if (ret)
> +		return ret;

scoped_cond_guard(mutex_intr, return -EINTR, pf_migration_mutex(xe, vfid)) ?

> +
> +	while (produced < len) {
> +		ret = vf_mig_data_write_single(xe, vfid, buf, len - produced);
> +		if (ret < 0) {
> +			mutex_unlock(pf_migration_mutex(xe, vfid));
> +			return ret;
> +		}
> +
> +		produced += ret;
> +		buf += ret;
> +	}
> +
> +	mutex_unlock(pf_migration_mutex(xe, vfid));
> +	return produced;
> +}
> +
> +#define MIGRATION_DESC_SIZE 4
> +static size_t pf_desc_init(struct xe_device *xe, unsigned int vfid)
> +{
> +	struct xe_sriov_pf_migration_data **desc = pf_pick_descriptor(xe, vfid);
> +	struct xe_sriov_pf_migration_data *data;
> +	int ret;
> +
> +	data = xe_sriov_pf_migration_data_alloc(xe);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	ret = xe_sriov_pf_migration_data_init(data, 0, 0, XE_SRIOV_MIG_DATA_DESCRIPTOR,
> +					      0, MIGRATION_DESC_SIZE);
> +	if (ret) {
> +		xe_sriov_pf_migration_data_free(data);
> +		return ret;
> +	}
> +
> +	*desc = data;
> +
> +	return 0;
> +}
> +
> +static void pf_pending_init(struct xe_device *xe, unsigned int vfid)
> +{
> +	struct xe_sriov_pf_migration_data **data = pf_pick_pending(xe, vfid);
> +
> +	*data = NULL;
> +}
> +
> +#define MIGRATION_TRAILER_SIZE 0
> +static int pf_trailer_init(struct xe_device *xe, unsigned int vfid)
> +{
> +	struct xe_sriov_pf_migration_data **trailer = pf_pick_trailer(xe, vfid);
> +	struct xe_sriov_pf_migration_data *data;
> +	int ret;
> +
> +	data = xe_sriov_pf_migration_data_alloc(xe);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	ret = xe_sriov_pf_migration_data_init(data, 0, 0, XE_SRIOV_MIG_DATA_TRAILER,
> +					      0, MIGRATION_TRAILER_SIZE);
> +	if (ret) {
> +		xe_sriov_pf_migration_data_free(data);
> +		return ret;
> +	}
> +
> +	*trailer = data;
> +
> +	return 0;
> +}
> +
> +/**
> + * xe_sriov_pf_migration_data_save_init() - Initialize the pending save migration data.
> + * @gt: the &struct xe_device
> + * @vfid: the VF identifier
> + *
> + * Return: 0 on success, -errno on failure
> + */
> +int xe_sriov_pf_migration_data_save_init(struct xe_device *xe, unsigned int vfid)
> +{
> +	int ret;
> +
> +	ret = mutex_lock_interruptible(pf_migration_mutex(xe, vfid));
> +	if (ret)
> +		return ret;
> +
> +	ret = pf_desc_init(xe, vfid);
> +	if (ret)
> +		goto out;
> +
> +	ret = pf_trailer_init(xe, vfid);
> +	if (ret)
> +		goto out;
> +
> +	pf_pending_init(xe, vfid);
> +
> +out:
> +	mutex_unlock(pf_migration_mutex(xe, vfid));
> +	return ret;
> +}
> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_migration_data.h b/drivers/gpu/drm/xe/xe_sriov_pf_migration_data.h
> index 1dde4cfcdbc47..5b96c7f224002 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf_migration_data.h
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf_migration_data.h
> @@ -28,5 +28,10 @@ void xe_sriov_pf_migration_data_free(struct xe_sriov_pf_migration_data *snapshot
>  int xe_sriov_pf_migration_data_init(struct xe_sriov_pf_migration_data *data, u8 tile_id, u8 gt_id,
>  				    unsigned int type, loff_t offset, size_t size);
>  int xe_sriov_pf_migration_data_init_from_hdr(struct xe_sriov_pf_migration_data *snapshot);
> +ssize_t xe_sriov_pf_migration_data_read(struct xe_device *xe, unsigned int vfid,
> +					char __user *buf, size_t len);
> +ssize_t xe_sriov_pf_migration_data_write(struct xe_device *xe, unsigned int vfid,
> +					 const char __user *buf, size_t len);
> +int xe_sriov_pf_migration_data_save_init(struct xe_device *xe, unsigned int vfid);
>  
>  #endif
> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_migration_types.h b/drivers/gpu/drm/xe/xe_sriov_pf_migration_types.h
> index 80fdea32b884a..c5d75bb7f39c0 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf_migration_types.h
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf_migration_types.h
> @@ -7,6 +7,7 @@
>  #define _XE_SRIOV_PF_MIGRATION_TYPES_H_
>  
>  #include <linux/types.h>
> +#include <linux/mutex_types.h>
>  #include <linux/wait.h>
>  
>  struct xe_sriov_pf_migration_data {
> @@ -32,6 +33,14 @@ struct xe_sriov_pf_migration_data {
>  struct xe_sriov_pf_migration {
>  	/** @wq: waitqueue used to avoid busy-waiting for snapshot production/consumption */
>  	wait_queue_head_t wq;
> +	/** @lock: Mutex protecting the migration data */
> +	struct mutex lock;
> +	/** @pending: currently processed data packet of VF resource */
> +	struct xe_sriov_pf_migration_data *pending;
> +	/** @trailer: data packet used to indicate the end of stream */
> +	struct xe_sriov_pf_migration_data *trailer;
> +	/** @descriptor: data packet containing the metadata describing the device */
> +	struct xe_sriov_pf_migration_data *descriptor;
>  };
>  
>  #endif