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mm/memory/fault: add THP fault handling for zone device private pages

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Implement CPU fault handling for zone device THP entries through
do_huge_pmd_device_private(), enabling transparent migration of
device-private large pages back to system memory on CPU access.

When the CPU accesses a zone device THP entry, the fault handler calls the
device driver's migrate_to_ram() callback to migrate the entire large page
back to system memory.

Link: https://lkml.kernel.org/r/20251001065707.920170-9-balbirs@nvidia.com
Signed-off-by: Balbir Singh <balbirs@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Ying Huang <ying.huang@linux.alibaba.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Mika Penttilä <mpenttil@redhat.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Francois Dugast <francois.dugast@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Balbir Singh 2025-10-01 16:56:59 +10:00 committed by Andrew Morton
parent a30b48bf1b
commit 4964099163
3 changed files with 48 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/huge_mm.h
View File

@ -481,6 +481,8 @@ static inline bool folio_test_pmd_mappable(struct folio *folio)
vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf);
vm_fault_t do_huge_pmd_device_private(struct vm_fault *vmf);
extern struct folio *huge_zero_folio;
extern unsigned long huge_zero_pfn;
@ -662,6 +664,11 @@ static inline vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
return 0;
}
static inline vm_fault_t do_huge_pmd_device_private(struct vm_fault *vmf)
{
return 0;
}
static inline bool is_huge_zero_folio(const struct folio *folio)
{
return false;

38
mm/huge_memory.c
View File

@ -1288,6 +1288,44 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
}
vm_fault_t do_huge_pmd_device_private(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
vm_fault_t ret = 0;
spinlock_t *ptl;
swp_entry_t swp_entry;
struct page *page;
struct folio *folio;
if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
vma_end_read(vma);
return VM_FAULT_RETRY;
}
ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(*vmf->pmd, vmf->orig_pmd))) {
spin_unlock(ptl);
return 0;
}
swp_entry = pmd_to_swp_entry(vmf->orig_pmd);
page = pfn_swap_entry_to_page(swp_entry);
folio = page_folio(page);
vmf->page = page;
vmf->pte = NULL;
if (folio_trylock(folio)) {
folio_get(folio);
spin_unlock(ptl);
ret = page_pgmap(page)->ops->migrate_to_ram(vmf);
folio_unlock(folio);
folio_put(folio);
} else {
spin_unlock(ptl);
}
return ret;
}
/*
* always: directly stall for all thp allocations
* defer: wake kswapd and fail if not immediately available

5
mm/memory.c
View File

@ -6345,8 +6345,9 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
vmf.orig_pmd = pmdp_get_lockless(vmf.pmd);
if (unlikely(is_swap_pmd(vmf.orig_pmd))) {
VM_BUG_ON(thp_migration_supported() &&
!is_pmd_migration_entry(vmf.orig_pmd));
if (is_pmd_device_private_entry(vmf.orig_pmd))
return do_huge_pmd_device_private(&vmf);
if (is_pmd_migration_entry(vmf.orig_pmd))
pmd_migration_entry_wait(mm, vmf.pmd);
return 0;