diff options
| -rw-r--r-- | include/linux/mm.h | 21 | ||||
| -rw-r--r-- | include/linux/mm_types.h | 9 | ||||
| -rw-r--r-- | mm/gup.c | 30 | ||||
| -rw-r--r-- | mm/huge_memory.c | 3 |
4 files changed, 49 insertions, 14 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 406ab9ea818f..34f9dba17c1a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3421,15 +3421,24 @@ static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags) * Indicates whether GUP can follow a PROT_NONE mapped page, or whether * a (NUMA hinting) fault is required. */ -static inline bool gup_can_follow_protnone(unsigned int flags) +static inline bool gup_can_follow_protnone(struct vm_area_struct *vma, + unsigned int flags) { /* - * FOLL_FORCE has to be able to make progress even if the VMA is - * inaccessible. Further, FOLL_FORCE access usually does not represent - * application behaviour and we should avoid triggering NUMA hinting - * faults. + * If callers don't want to honor NUMA hinting faults, no need to + * determine if we would actually have to trigger a NUMA hinting fault. */ - return flags & FOLL_FORCE; + if (!(flags & FOLL_HONOR_NUMA_FAULT)) + return true; + + /* + * NUMA hinting faults don't apply in inaccessible (PROT_NONE) VMAs. + * + * Requiring a fault here even for inaccessible VMAs would mean that + * FOLL_FORCE cannot make any progress, because handle_mm_fault() + * refuses to process NUMA hinting faults in inaccessible VMAs. + */ + return !vma_is_accessible(vma); } typedef int (*pte_fn_t)(pte_t *pte, unsigned long addr, void *data); diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5e74ce4a28cd..7d30dc4ff0ff 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1286,6 +1286,15 @@ enum { FOLL_PCI_P2PDMA = 1 << 10, /* allow interrupts from generic signals */ FOLL_INTERRUPTIBLE = 1 << 11, + /* + * Always honor (trigger) NUMA hinting faults. + * + * FOLL_WRITE implicitly honors NUMA hinting faults because a + * PROT_NONE-mapped page is not writable (exceptions with FOLL_FORCE + * apply). get_user_pages_fast_only() always implicitly honors NUMA + * hinting faults. + */ + FOLL_HONOR_NUMA_FAULT = 1 << 12, /* See also internal only FOLL flags in mm/internal.h */ }; @@ -597,7 +597,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, pte = ptep_get(ptep); if (!pte_present(pte)) goto no_page; - if (pte_protnone(pte) && !gup_can_follow_protnone(flags)) + if (pte_protnone(pte) && !gup_can_follow_protnone(vma, flags)) goto no_page; page = vm_normal_page(vma, address, pte); @@ -714,7 +714,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, if (likely(!pmd_trans_huge(pmdval))) return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); - if (pmd_protnone(pmdval) && !gup_can_follow_protnone(flags)) + if (pmd_protnone(pmdval) && !gup_can_follow_protnone(vma, flags)) return no_page_table(vma, flags); ptl = pmd_lock(mm, pmd); @@ -851,6 +851,10 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, if (WARN_ON_ONCE(foll_flags & FOLL_PIN)) return NULL; + /* + * We never set FOLL_HONOR_NUMA_FAULT because callers don't expect + * to fail on PROT_NONE-mapped pages. + */ page = follow_page_mask(vma, address, foll_flags, &ctx); if (ctx.pgmap) put_dev_pagemap(ctx.pgmap); @@ -2227,6 +2231,13 @@ static bool is_valid_gup_args(struct page **pages, int *locked, gup_flags |= FOLL_UNLOCKABLE; } + /* + * For now, always trigger NUMA hinting faults. Some GUP users like + * KVM require the hint to be as the calling context of GUP is + * functionally similar to a memory reference from task context. + */ + gup_flags |= FOLL_HONOR_NUMA_FAULT; + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ if (WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) == (FOLL_PIN | FOLL_GET))) @@ -2551,7 +2562,14 @@ static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, struct page *page; struct folio *folio; - if (pte_protnone(pte) && !gup_can_follow_protnone(flags)) + /* + * Always fallback to ordinary GUP on PROT_NONE-mapped pages: + * pte_access_permitted() better should reject these pages + * either way: otherwise, GUP-fast might succeed in + * cases where ordinary GUP would fail due to VMA access + * permissions. + */ + if (pte_protnone(pte)) goto pte_unmap; if (!pte_access_permitted(pte, flags & FOLL_WRITE)) @@ -2970,8 +2988,8 @@ static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned lo if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) || pmd_devmap(pmd))) { - if (pmd_protnone(pmd) && - !gup_can_follow_protnone(flags)) + /* See gup_pte_range() */ + if (pmd_protnone(pmd)) return 0; if (!gup_huge_pmd(pmd, pmdp, addr, next, flags, @@ -3151,7 +3169,7 @@ static int internal_get_user_pages_fast(unsigned long start, if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | FOLL_FORCE | FOLL_PIN | FOLL_GET | FOLL_FAST_ONLY | FOLL_NOFAULT | - FOLL_PCI_P2PDMA))) + FOLL_PCI_P2PDMA | FOLL_HONOR_NUMA_FAULT))) return -EINVAL; if (gup_flags & FOLL_PIN) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index eb3678360b97..f15d557e5708 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1467,8 +1467,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) return ERR_PTR(-EFAULT); - /* Full NUMA hinting faults to serialise migration in fault paths */ - if (pmd_protnone(*pmd) && !gup_can_follow_protnone(flags)) + if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags)) return NULL; if (!pmd_write(*pmd) && gup_must_unshare(vma, flags, page)) |