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drm/pagemap: Prevent double migration of device pages

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A device-private folio migrated to system memory by a CPU fault can
remain reachable through the raw-PFN eviction path until migration
finalization drops the source reference.

If eviction selects the same device-private folio during this window,
it can attempt to migrate the folio again. The second migration can leave
an uncharged folio on an LRU list, causing folio_lruvec_lock_irqsave() to
retry indefinitely and resulting in a soft lockup and RCU stall.

Mark successfully migrated device-private folios using a low bit of
their zone_device_data before migration finalization. Make both CPU-fault
and raw-PFN migration paths skip device-private folios carrying this
flag.

Mask the flag when retrieving the drm_pagemap_zdd pointer and preserve
it when a device-private folio is split. Keeping the state on the physical
folio also avoids depending on a virtual address that may change before a
fault occurs.

v2:
- Replace the retired-PFN XArray with an embedded bitmap. (Matthew Brost)
- Mark every base page covered by a migrated folio so retirement remains
  valid if the folio is later split.

v3:
- Store the migrated state in a low bit of zone_device_data instead of
  adding virtual-range and bitmap tracking to the ZDD. (Matthew Brost)
- Mask the flag when retrieving the ZDD and preserve it when splitting
  a folio.
- Drop the pre-existing fixes already covered by Matthew Brost's series:
  https://patchwork.freedesktop.org/series/171651/

v4:
- Advance by the folio size only for migration entries marked with
  MIGRATE_PFN_COMPOUND. (Sashiko)

v5:
- Simplify ZDD flag updates and folio iteration. (Matthew Brost)
- Skip retired device-private folios in the CPU-fault path. (Matthew Brost)
- Preserve flag bits while taking a new ZDD reference for split folios.

v6:
- Restore MIGRATE_PFN_COMPOUND-aware stepping so non-compound migration
  entries are processed one at a time. (Sashiko)
- Drop the pre-existing fixes already covered by Matthew Brost's series:
  https://patchwork.freedesktop.org/series/171651/

The lockup was observed as:
[10109.860465] watchdog: BUG: soft lockup - CPU#9 stuck for 26s! [kworker/u65:5:6557]
[10109.860524] Tainted: [S]=CPU_OUT_OF_SPEC, [O]=OOT_MODULE
[10109.860524] Hardware name: ASUS System Product Name/PRIME Z790-P WIFI, BIOS 0812 02/24/2023
[10109.860525] Workqueue: xe_page_fault_work_queue xe_pagefault_queue_work [xe]
[10109.860644] RIP: 0010:_raw_spin_unlock_irqrestore+0x57/0x80
[10109.860655] Call Trace:
[10109.860655]  <TASK>
[10109.860657]  folio_lruvec_lock_irqsave+0x216/0x220
[10109.860661]  ? __pfx_lru_add+0x10/0x10
[10109.860665]  folio_batch_move_lru+0xc8/0x450
[10109.860670]  ? lock_acquire+0xc4/0x2d0
[10109.860674]  ? __folio_batch_add_and_move+0x60/0x2e0
[10109.860677]  ? folio_migrate_mapping+0xa6/0x110
[10109.860679]  ? folio_migrate_flags+0x13b/0x1b0
[10109.860681]  ? __pfx_lru_add+0x10/0x10
[10109.860683]  __folio_batch_add_and_move+0xe7/0x2e0
[10109.860685]  ? dma_iova_try_alloc+0xb0/0x140
[10109.860689]  folio_add_lru+0x64/0x80
[10109.860691]  __migrate_device_finalize+0x12c/0x270
[10109.860695]  migrate_device_finalize+0x10/0x20
[10109.860698]  drm_pagemap_evict_to_ram+0x185/0x370 [drm_gpusvm_helper]
[10109.860704]  ? drm_pagemap_evict_to_ram+0x96/0x370 [drm_gpusvm_helper]
[10109.860709]  xe_svm_bo_evict+0x15/0x20 [xe]
[10109.860819]  ? xe_svm_bo_evict+0x15/0x20 [xe]
[10109.860921]  xe_bo_move+0x107e/0x1570 [xe]
[10109.860992]  ? xe_ttm_tt_create+0x168/0x340 [xe]
[10109.861059]  ? __up_read+0x98/0x2b0
[10109.861061]  ? lock_is_held_type+0xa3/0x130
[10109.861067]  ttm_bo_handle_move_mem+0xe8/0x1e0 [ttm]
[10109.861075]  ttm_bo_evict+0x141/0x1c0 [ttm]
[10109.861081]  ttm_bo_evict_cb+0x9f/0x100 [ttm]
[10109.861086]  ttm_lru_walk_for_evict+0x84/0x190 [ttm]
[10109.861091]  ? xe_ttm_vram_mgr_new+0x258/0x3a0 [xe]
[10109.861198]  ttm_bo_alloc_resource+0x219/0x750 [ttm]
[10109.861203]  ? ttm_bo_alloc_resource+0xa9/0x750 [ttm]
[10109.861208]  ? lock_acquire+0xc4/0x2d0
[10109.861214]  ttm_bo_validate+0x94/0x1c0 [ttm]
[10109.861218]  ? ww_mutex_trylock+0x19d/0x3d0
[10109.861219]  ? _raw_write_unlock+0x22/0x50
[10109.861223]  ttm_bo_init_reserved+0x17d/0x1f0 [ttm]
[10109.861228]  xe_bo_init_locked+0x20a/0x620 [xe]
[10109.861294]  ? __pfx_xe_ttm_bo_destroy+0x10/0x10 [xe]
[10109.861359]  ? mark_held_locks+0x46/0x90
[10109.861361]  ? __create_object+0x68/0xc0
[10109.861366]  __xe_bo_create_locked+0x384/0xa20 [xe]
[10109.861432]  ? lock_acquire+0xc4/0x2d0
[10109.861434]  ? xe_drm_pagemap_populate_mm+0xd3/0x340 [xe]
[10109.861542]  xe_bo_create_locked+0x23/0x40 [xe]
[10109.861609]  xe_drm_pagemap_populate_mm+0x12e/0x340 [xe]
[10109.861707]  ? __lock_acquire+0x43e/0x2930
[10109.861716]  drm_pagemap_populate_mm+0x74/0xe0 [drm_gpusvm_helper]
[10109.861720]  xe_svm_alloc_vram+0xb5/0x2c0 [xe]
[10109.861817]  ? seqcount_lockdep_reader_access.constprop.0+0x9f/0xc0
[10109.861819]  ? ktime_get+0x23/0x130
[10109.861821]  ? trace_hardirqs_on+0x22/0xe0
[10109.861823]  ? seqcount_lockdep_reader_access.constprop.0+0x9f/0xc0
[10109.861826]  __xe_svm_handle_pagefault+0x77d/0xbf0 [xe]
[10109.861924]  ? rwsem_down_write_slowpath+0x43a/0x9a0
[10109.861926]  ? _raw_spin_unlock_irq+0x27/0x70
[10109.861928]  ? rwsem_down_write_slowpath+0x43a/0x9a0
[10109.861929]  ? trace_hardirqs_on+0x22/0xe0
[10109.861931]  ? _raw_spin_unlock_irq+0x27/0x70
[10109.861933]  ? rwsem_down_write_slowpath+0x459/0x9a0
[10109.861937]  xe_svm_handle_pagefault+0x3d/0xb0 [xe]
[10109.862030]  xe_pagefault_queue_work+0x1a9/0x520 [xe]
[10109.862122]  process_one_work+0x239/0x730
[10109.862127]  worker_thread+0x200/0x3f0
[10109.862130]  ? __pfx_worker_thread+0x10/0x10
[10109.862132]  kthread+0x10d/0x150
[10109.862133]  ? __pfx_kthread+0x10/0x10
[10109.862135]  ret_from_fork+0x3bd/0x470
[10109.862138]  ? __pfx_kthread+0x10/0x10
[10109.862140]  ret_from_fork_asm+0x1a/0x30
[10109.862146]  </TASK>

Fixes: 99624bdff8 ("drm/gpusvm: Add support for GPU Shared Virtual Memory")
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Assisted-by: Claude:claude-opus-4-8
Suggested-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260810092845.2776097-1-arvind.yadav@intel.com
This commit is contained in:
Arvind Yadav
2026-08-10 14:58:45 +05:30
committed by Matthew Brost
parent be150d3586
commit c4126f1db3
2 changed files with 129 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

127
drivers/gpu/drm/drm_pagemap.c
View File

@@ -1102,12 +1102,117 @@ void drm_pagemap_put(struct drm_pagemap *dpagemap)
}
EXPORT_SYMBOL(drm_pagemap_put);
/**
* drm_pagemap_page_get_flags() - Read flags from a device-private folio
* @page: Pointer to a page of the device-private folio
*
* Return: The DRM_PAGEMAP_ZDD_FLAG_* bits encoded in zone_device_data.
*/
static unsigned long drm_pagemap_page_get_flags(struct page *page)
{
struct folio *folio = page_folio(page);
return (unsigned long)folio_zone_device_data(folio) &
DRM_PAGEMAP_ZDD_FLAG_MASK;
}
/**
* drm_pagemap_page_set_flags() - Set flags on a device-private folio
* @page: Pointer to a page of the device-private folio
* @flags: DRM_PAGEMAP_ZDD_FLAG_* bits to set
*
* Preserve any flags already encoded alongside the ZDD pointer.
*/
static void drm_pagemap_page_set_flags(struct page *page,
unsigned long flags)
{
struct folio *folio = page_folio(page);
unsigned long old;
if (WARN_ON_ONCE(flags & ~DRM_PAGEMAP_ZDD_FLAG_MASK))
return;
old = (unsigned long)folio_zone_device_data(folio);
folio_set_zone_device_data(folio, (void *)(old | flags));
}
/**
* drm_pagemap_retire_migrated_pages() - Record migrated device-private folios
* @src_pfns: source array after migrate_vma_pages() or migrate_device_pages()
* @npages: number of entries in @src_pfns
*
* Flag device-private folios successfully migrated to RAM before finalize
* unlocks the sources. The migrated state is stored in the physical folio, so
* it survives later folio splits and subsequent migrations can skip it.
*/
static void drm_pagemap_retire_migrated_pages(unsigned long *src_pfns,
unsigned long npages)
{
unsigned long i = 0;
while (i < npages) {
struct page *page = migrate_pfn_to_page(src_pfns[i]);
unsigned long nr = 1;
if (!page) {
i++;
continue;
}
if (src_pfns[i] & MIGRATE_PFN_COMPOUND)
nr = folio_nr_pages(page_folio(page));
if ((src_pfns[i] & MIGRATE_PFN_MIGRATE) &&
is_device_private_page(page))
drm_pagemap_page_set_flags(page,
DRM_PAGEMAP_ZDD_FLAG_MIGRATED);
i += nr;
}
}
/**
* drm_pagemap_skip_retired_pages() - Skip retired device-private folios
* @src_pfns: MIGRATE_PFN-encoded source array
* @npages: number of entries in @src_pfns
*
* Skip source folios already migrated to RAM, identified by the migrated flag
* stored in the physical folio's zone_device_data.
*/
static void drm_pagemap_skip_retired_pages(unsigned long *src_pfns,
unsigned long npages)
{
unsigned long i = 0;
while (i < npages) {
struct page *page = migrate_pfn_to_page(src_pfns[i]);
unsigned long nr = 1;
if (!page) {
i++;
continue;
}
if (src_pfns[i] & MIGRATE_PFN_COMPOUND)
nr = folio_nr_pages(page_folio(page));
if ((src_pfns[i] & MIGRATE_PFN_MIGRATE) &&
is_device_private_page(page) &&
(drm_pagemap_page_get_flags(page) &
DRM_PAGEMAP_ZDD_FLAG_MIGRATED))
src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
i += nr;
}
}
/**
* drm_pagemap_evict_to_ram() - Evict GPU SVM range to RAM
* @devmem_allocation: Pointer to the device memory allocation
*
* Similar to __drm_pagemap_migrate_to_ram but does not require mmap lock and
* migration done via migrate_device_* functions.
* Similar to __drm_pagemap_migrate_to_ram(), but uses the
* migrate_device_* helpers and does not require the mmap lock.
* Device-private PFNs already migrated to RAM by either path are skipped.
*
* Return: 0 on success, negative error code on failure.
*/
@@ -1148,6 +1253,8 @@ int drm_pagemap_evict_to_ram(struct drm_pagemap_devmem *devmem_allocation)
if (err)
goto err_free;
drm_pagemap_skip_retired_pages(src, npages);
err = drm_pagemap_migrate_populate_ram_pfn(NULL, NULL, npages, &mpages,
src, dst, 0);
if (err || !mpages)
@@ -1178,6 +1285,7 @@ int drm_pagemap_evict_to_ram(struct drm_pagemap_devmem *devmem_allocation)
if (err)
drm_pagemap_migration_unlock_put_pages(npages, dst);
migrate_device_pages(src, dst, npages);
drm_pagemap_retire_migrated_pages(src, npages);
migrate_device_finalize(src, dst, npages);
drm_pagemap_migrate_unmap_pages(devmem_allocation->dev, pagemap_addr, dst, npages,
DMA_FROM_DEVICE, &state);
@@ -1275,13 +1383,15 @@ static int __drm_pagemap_migrate_to_ram(struct vm_area_struct *vas,
if (!migrate.cpages)
goto err_free;
drm_pagemap_skip_retired_pages(migrate.src, npages);
ops = zdd->devmem_allocation->ops;
dev = zdd->devmem_allocation->dev;
err = drm_pagemap_migrate_populate_ram_pfn(vas, page, npages, &mpages,
migrate.src, migrate.dst,
start);
if (err)
if (err || !mpages)
goto err_finalize;
err = drm_pagemap_migrate_map_system_pages(dev, pagemap_addr,
@@ -1308,6 +1418,7 @@ static int __drm_pagemap_migrate_to_ram(struct vm_area_struct *vas,
if (err)
drm_pagemap_migration_unlock_put_pages(npages, migrate.dst);
migrate_vma_pages(&migrate);
drm_pagemap_retire_migrated_pages(migrate.src, npages);
migrate_vma_finalize(&migrate);
if (dev)
drm_pagemap_migrate_unmap_pages(dev, pagemap_addr, migrate.dst,
@@ -1360,13 +1471,19 @@ static vm_fault_t drm_pagemap_migrate_to_ram(struct vm_fault *vmf)
static void drm_pagemap_folio_split(struct folio *orig_folio, struct folio *new_folio)
{
struct drm_pagemap_zdd *zdd;
unsigned long orig_data, new_data;
if (!new_folio)
return;
new_folio->pgmap = orig_folio->pgmap;
zdd = folio_zone_device_data(orig_folio);
folio_set_zone_device_data(new_folio, drm_pagemap_zdd_get(zdd));
orig_data = (unsigned long)folio_zone_device_data(orig_folio);
zdd = (struct drm_pagemap_zdd *)(orig_data & ~DRM_PAGEMAP_ZDD_FLAG_MASK);
new_data = (unsigned long)drm_pagemap_zdd_get(zdd);
new_data |= orig_data & DRM_PAGEMAP_ZDD_FLAG_MASK;
folio_set_zone_device_data(new_folio, (void *)new_data);
}
static const struct dev_pagemap_ops drm_pagemap_pagemap_ops = {

8
include/drm/drm_pagemap.h
View File

@@ -2,6 +2,7 @@
#ifndef _DRM_PAGEMAP_H_
#define _DRM_PAGEMAP_H_
#include <linux/bits.h>
#include <linux/dma-direction.h>
#include <linux/hmm.h>
#include <linux/memremap.h>
@@ -339,6 +340,9 @@ struct drm_pagemap_migrate_details {
#if IS_ENABLED(CONFIG_ZONE_DEVICE)
#define DRM_PAGEMAP_ZDD_FLAG_MIGRATED BIT(0)
#define DRM_PAGEMAP_ZDD_FLAG_MASK DRM_PAGEMAP_ZDD_FLAG_MIGRATED
int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem *devmem_allocation,
struct mm_struct *mm,
unsigned long start, unsigned long end,
@@ -373,7 +377,9 @@ static inline struct drm_pagemap_zdd *drm_pagemap_page_zone_device_data(struct p
{
struct folio *folio = page_folio(page);
return folio_zone_device_data(folio);
return (struct drm_pagemap_zdd *)
((unsigned long)folio_zone_device_data(folio) &
~DRM_PAGEMAP_ZDD_FLAG_MASK);
}
#else