Re: [PATCH V16 10/12] drm/xe: Add sysfs interface for bad gpu vram pages

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

On 8/17/2026 8:51 AM, Tejas Upadhyay wrote:
> Include a sysfs interface designed to expose information about bad
> VRAM pages — those identified as having hardware faults (e.g., ECC
> errors). This interface allows userspace tools and administrators to
> monitor the health of the GPU's local memory and track the status of
> page retirement. Details on bad gpu vram pages can be found under
> /sys/bus/pci/devices/<bdf>/vram_bad_pages.

since those new files are xe driver specific, shouldn't we refer to
them using

	/sys/bus/pci/drivers/xe/<bdf>/vram...

> 
> The format is: pfn : gpu_page_size : flags

kernel documentation [1] says

	"Mixing types, expressing multiple lines of data, and doing
	fancy formatting of data is heavily frowned upon"

[1] https://docs.kernel.org/filesystems/sysfs.html#attributes

so to follow the guidelines maybe we expose the separate files:

/sys/bus/pci/drivers/xe/<bdf>/vram_page_size		u64
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_count	u64
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_reserved	u64[]
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_pending	u64[]
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_failed	u64[]

or

/sys/bus/pci/drivers/xe/<bdf>
|
+-- vram/
    +-- page_size	u64
    +-- bad_pages/
        +-- count	u64
        +-- reserved	u64[]
        +-- pending	u64[]
        +-- failed	u64[]

then 

/sys/bus/pci/drivers/xe/<bdf>/vram_page_size:0x1000
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_count:5
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_reserved:0x0000000000000000
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_pending:0x0000000001234000
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_pending:0x0000000001235000
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_pending:0x0000000001236000
/sys/bus/pci/drivers/xe/<bdf>/vram_bad_pages_pending:0x0000000001237000

> 
> flags:
>   R: reserved, this gpu page is reserved.
>   P: pending for reserve, this gpu page is marked as bad, will be
>      reserved in next window of page_reserve.
>   F: unable to reserve, this gpu page can't be reserved due to some
>      reasons.
> 
> For example, cat /sys/bus/pci/devices/<bdf>/vram_bad_pages:
>   max_pages : 10000
>   0x0000000000000000 : 0x0000000000001000 : R
>   0x0000000000001234 : 0x0000000000001000 : P
> 
> The sysfs binary attribute is created under the PCI device kobject
> when the platform supports it and the configfs bad_page_reservation
> policy is enabled. Uses RCU-protected list traversal so reads never
> block normal VRAM allocation operations.
> 
> Signed-off-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_device_sysfs.c       |   7 +
>  drivers/gpu/drm/xe/xe_ttm_vram_mgr.c       | 141 +++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_ttm_vram_mgr.h       |   1 +
>  drivers/gpu/drm/xe/xe_ttm_vram_mgr_types.h |   2 +
>  4 files changed, 151 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_device_sysfs.c b/drivers/gpu/drm/xe/xe_device_sysfs.c
> index a73e0e957cb0..47c5be4180fe 100644
> --- a/drivers/gpu/drm/xe/xe_device_sysfs.c
> +++ b/drivers/gpu/drm/xe/xe_device_sysfs.c
> @@ -8,12 +8,14 @@
>  #include <linux/pci.h>
>  #include <linux/sysfs.h>
>  
> +#include "xe_configfs.h"
>  #include "xe_device.h"
>  #include "xe_device_sysfs.h"
>  #include "xe_mmio.h"
>  #include "xe_pcode_api.h"
>  #include "xe_pcode.h"
>  #include "xe_pm.h"
> +#include "xe_ttm_vram_mgr.h"
>  
>  /**
>   * DOC: Xe device sysfs
> @@ -267,6 +269,7 @@ static const struct attribute_group auto_link_downgrade_attr_group = {
>  int xe_device_sysfs_init(struct xe_device *xe)
>  {
>  	struct device *dev = xe->drm.dev;
> +	bool policy;
>  	int ret;
>  
>  	if (xe->d3cold.capable) {
> @@ -285,5 +288,9 @@ int xe_device_sysfs_init(struct xe_device *xe)
>  			return ret;
>  	}
>  
> +	policy = xe_configfs_get_bad_page_reservation(to_pci_dev(dev));
> +	if (xe->info.platform == XE_CRESCENTISLAND && policy)
> +		xe_ttm_vram_sysfs_init(xe);
> +
>  	return 0;
>  }
> diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
> index a48196ce303f..73cd06c22d37 100644
> --- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
> +++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
> @@ -820,3 +820,144 @@ int xe_ttm_vram_handle_addr_fault(struct xe_device *xe, u64 addr)
>  	return xe_ttm_vram_reserve_page_at_addr(xe, addr - vr->dpa_base, vram_mgr, mm);
>  }
>  EXPORT_SYMBOL(xe_ttm_vram_handle_addr_fault);
> +
> +static size_t serialize_bad_pages(struct xe_ttm_vram_mgr *mgr, char *buf, size_t max_len)
> +{
> +	struct xe_ttm_vram_offline_resource *pos;
> +	struct gpu_buddy_block *block;
> +	size_t s = 0;
> +	int printed;
> +	int count = 0;
> +
> +	rcu_read_lock();
> +
> +	printed = scnprintf(buf + s, max_len - s, "max_pages: %d\n", mgr->max_pages);
> +	s += printed;
> +
> +	list_for_each_entry_rcu(pos, &mgr->offlined_pages, offlined_link) {
> +		if (count >= 10000 || s >= max_len)
> +			break;
> +
> +		block = list_first_entry_or_null(&pos->blocks, struct gpu_buddy_block, link);
> +		if (!block)
> +			continue;
> +
> +		printed = scnprintf(buf + s, max_len - s, "0x%016llx : 0x%016llx : %c\n",
> +				    gpu_buddy_block_offset(block) >> PAGE_SHIFT,
> +				    gpu_buddy_block_size(&mgr->mm, block), 'R');
> +		s += printed;
> +		count++;
> +	}
> +	list_for_each_entry_rcu(pos, &mgr->queued_pages, queued_link) {
> +		u64 pfn, blk_size;
> +
> +		if (count >= 10000 || s >= max_len)
> +			break;
> +
> +		block = list_first_entry_or_null(&pos->blocks, struct gpu_buddy_block, link);
> +		if (block) {
> +			pfn = gpu_buddy_block_offset(block) >> PAGE_SHIFT;
> +			blk_size = gpu_buddy_block_size(&mgr->mm, block);
> +		} else {
> +			pfn = pos->addr >> PAGE_SHIFT;
> +			blk_size = PAGE_SIZE;
> +		}
> +
> +		printed = scnprintf(buf + s, max_len - s, "0x%016llx : 0x%016llx : %c\n",
> +				    pfn, blk_size, pos->status ? 'F' : 'P');
> +		s += printed;
> +		count++;
> +	}
> +
> +	rcu_read_unlock();
> +	return s;
> +}
> +
> +static ssize_t vram_bad_pages_bin_read(struct file *filp, struct kobject *kobj,
> +				       const struct bin_attribute *attr, char *buf,
> +				       loff_t off, size_t count)
> +{
> +	struct device *dev = kobj_to_dev(kobj);
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	struct ttm_resource_manager *man;
> +	struct xe_ttm_vram_mgr *mgr;
> +	size_t allocation_size;
> +	struct xe_device *xe;
> +	size_t full_data_len;
> +	int active_entries;
> +	char *temp_buf;
> +
> +	xe = pdev_to_xe_device(pdev);
> +	man = ttm_manager_type(&xe->ttm, XE_PL_VRAM0);
> +	if (!man)
> +		return -ENODEV;
> +	mgr = to_xe_ttm_vram_mgr(man);
> +
> +	active_entries = READ_ONCE(mgr->n_offlined_pages) + READ_ONCE(mgr->n_queued_pages);
> +
> +	if (active_entries > 10000)
> +		active_entries = 10000;
> +
> +	allocation_size = 64 + (active_entries * 48);
> +
> +	temp_buf = kvmalloc(allocation_size, GFP_KERNEL);
> +	if (!temp_buf)
> +		return -ENOMEM;
> +
> +	/* serialize_bad_pages uses rcu_read_lock internally */
> +	full_data_len = serialize_bad_pages(mgr, temp_buf, allocation_size);
> +
> +	if (off >= full_data_len) {
> +		kvfree(temp_buf);
> +		return 0;
> +	}
> +
> +	if (off + count > full_data_len)
> +		count = full_data_len - off;
> +
> +	memcpy(buf, temp_buf + off, count);
> +
> +	kvfree(temp_buf);
> +	return count;
> +}
> +
> +static const struct bin_attribute bin_attr_vram_bad_pages = {
> +	.attr = { .name = "vram_bad_pages", .mode = 0444 },
> +	.read = vram_bad_pages_bin_read,
> +	.size = 0,
> +};
> +
> +static void xe_ttm_vram_sysfs_fini(void *arg)
> +{
> +	struct xe_device *xe = arg;
> +	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
> +
> +	sysfs_remove_bin_file(&pdev->dev.kobj, &bin_attr_vram_bad_pages);
> +}
> +
> +/**
> + * xe_ttm_vram_sysfs_init - Initialize vram bad pages sysfs binary file
> + * @xe: Xe Device object
> + *
> + * Creates a binary sysfs file under the PCI device for reading
> + * offlined and queued VRAM pages. Supports large entry counts
> + * via offset/count pagination.
> + *
> + * Returns: 0 on success, negative error code on error.
> + */
> +int xe_ttm_vram_sysfs_init(struct xe_device *xe)
> +{
> +	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
> +	int err;
> +
> +	err = sysfs_create_bin_file(&pdev->dev.kobj, &bin_attr_vram_bad_pages);
> +	if (err) {
> +		dev_err(&pdev->dev,
> +			"Failed to create vram_bad_pages sysfs: %d\n",
> +			err);
> +		return err;
> +	}
> +
> +	return devm_add_action_or_reset(&pdev->dev, xe_ttm_vram_sysfs_fini, xe);
> +}
> +EXPORT_SYMBOL(xe_ttm_vram_sysfs_init);
> diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h
> index d5392beff30c..eb55b0f74ef3 100644
> --- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h
> +++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h
> @@ -32,6 +32,7 @@ void xe_ttm_vram_get_used(struct ttm_resource_manager *man,
>  			  u64 *used, u64 *used_visible);
>  
>  int xe_ttm_vram_handle_addr_fault(struct xe_device *xe, u64 addr);
> +int xe_ttm_vram_sysfs_init(struct xe_device *xe);
>  static inline struct xe_ttm_vram_mgr_resource *
>  to_xe_ttm_vram_mgr_resource(struct ttm_resource *res)
>  {
> diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr_types.h b/drivers/gpu/drm/xe/xe_ttm_vram_mgr_types.h
> index dc97b0ad0e51..efcf3e1d4e80 100644
> --- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr_types.h
> +++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr_types.h
> @@ -37,6 +37,8 @@ struct xe_ttm_vram_mgr {
>  	struct mutex lock;
>  	/** @mem_type: The TTM memory type */
>  	u32 mem_type;
> +	/** @max_pages: max pages that can be in offline queue retrieved from FW */
> +	u16 max_pages;
>  };
>  
>  /**