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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D132310000D X-Stat-Signature: bbn1ira3mh79qqws541718na3jmc8eq7 X-HE-Tag: 1747127453-266688 X-HE-Meta: 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 TTn3ZYkW 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 12.05.25 18:42, Lorenzo Stoakes wrote: > On Mon, May 12, 2025 at 02:34:17PM +0200, David Hildenbrand wrote: >> Let's use our new interface. In remap_pfn_range(), we'll now decide >> whether we have to track (full VMA covered) or only lookup the >> cachemode (partial VMA covered). >> >> Remember what we have to untrack by linking it from the VMA. When >> duplicating VMAs (e.g., splitting, mremap, fork), we'll handle it similar >> to anon VMA names, and use a kref to share the tracking. >> >> Once the last VMA un-refs our tracking data, we'll do the untracking, >> which simplifies things a lot and should sort our various issues we saw >> recently, for example, when partially unmapping/zapping a tracked VMA. >> >> This change implies that we'll keep tracking the original PFN range even >> after splitting + partially unmapping it: not too bad, because it was >> not working reliably before. The only thing that kind-of worked before >> was shrinking such a mapping using mremap(): we managed to adjust the >> reservation in a hacky way, now we won't adjust the reservation but >> leave it around until all involved VMAs are gone. >> >> If that ever turns out to be an issue, we could hook into VM splitting >> code and split the tracking; however, that adds complexity that might >> not be required, so we'll keep it simple for now. >> >> Acked-by: Ingo Molnar # x86 bits >> Signed-off-by: David Hildenbrand > > Other than small nit below, > > Reviewed-by: Lorenzo Stoakes > >> --- >> include/linux/mm_inline.h | 2 + >> include/linux/mm_types.h | 11 ++++++ >> mm/memory.c | 82 +++++++++++++++++++++++++++++++-------- >> mm/mmap.c | 5 --- >> mm/mremap.c | 4 -- >> mm/vma_init.c | 50 ++++++++++++++++++++++++ >> 6 files changed, 129 insertions(+), 25 deletions(-) >> >> diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h >> index f9157a0c42a5c..89b518ff097e6 100644 >> --- a/include/linux/mm_inline.h >> +++ b/include/linux/mm_inline.h >> @@ -447,6 +447,8 @@ static inline bool anon_vma_name_eq(struct anon_vma_name *anon_name1, >> >> #endif /* CONFIG_ANON_VMA_NAME */ >> >> +void pfnmap_track_ctx_release(struct kref *ref); >> + >> static inline void init_tlb_flush_pending(struct mm_struct *mm) >> { >> atomic_set(&mm->tlb_flush_pending, 0); >> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h >> index 15808cad2bc1a..3e934dc6057c4 100644 >> --- a/include/linux/mm_types.h >> +++ b/include/linux/mm_types.h >> @@ -763,6 +763,14 @@ struct vma_numab_state { >> int prev_scan_seq; >> }; >> >> +#ifdef __HAVE_PFNMAP_TRACKING >> +struct pfnmap_track_ctx { >> + struct kref kref; >> + unsigned long pfn; >> + unsigned long size; /* in bytes */ >> +}; >> +#endif >> + >> /* >> * Describes a VMA that is about to be mmap()'ed. Drivers may choose to >> * manipulate mutable fields which will cause those fields to be updated in the >> @@ -900,6 +908,9 @@ struct vm_area_struct { >> struct anon_vma_name *anon_name; >> #endif >> struct vm_userfaultfd_ctx vm_userfaultfd_ctx; >> +#ifdef __HAVE_PFNMAP_TRACKING >> + struct pfnmap_track_ctx *pfnmap_track_ctx; >> +#endif >> } __randomize_layout; >> >> #ifdef CONFIG_NUMA >> diff --git a/mm/memory.c b/mm/memory.c >> index 064fc55d8eab9..4cf4adb0de266 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -1371,7 +1371,7 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) >> struct mm_struct *dst_mm = dst_vma->vm_mm; >> struct mm_struct *src_mm = src_vma->vm_mm; >> struct mmu_notifier_range range; >> - unsigned long next, pfn = 0; >> + unsigned long next; >> bool is_cow; >> int ret; >> >> @@ -1381,12 +1381,6 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) >> if (is_vm_hugetlb_page(src_vma)) >> return copy_hugetlb_page_range(dst_mm, src_mm, dst_vma, src_vma); >> >> - if (unlikely(src_vma->vm_flags & VM_PFNMAP)) { >> - ret = track_pfn_copy(dst_vma, src_vma, &pfn); >> - if (ret) >> - return ret; >> - } >> - >> /* >> * We need to invalidate the secondary MMU mappings only when >> * there could be a permission downgrade on the ptes of the >> @@ -1428,8 +1422,6 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) >> raw_write_seqcount_end(&src_mm->write_protect_seq); >> mmu_notifier_invalidate_range_end(&range); >> } >> - if (ret && unlikely(src_vma->vm_flags & VM_PFNMAP)) >> - untrack_pfn_copy(dst_vma, pfn); >> return ret; >> } >> >> @@ -1924,9 +1916,6 @@ static void unmap_single_vma(struct mmu_gather *tlb, >> if (vma->vm_file) >> uprobe_munmap(vma, start, end); >> >> - if (unlikely(vma->vm_flags & VM_PFNMAP)) >> - untrack_pfn(vma, 0, 0, mm_wr_locked); >> - >> if (start != end) { >> if (unlikely(is_vm_hugetlb_page(vma))) { >> /* >> @@ -2872,6 +2861,36 @@ int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr, >> return error; >> } >> >> +#ifdef __HAVE_PFNMAP_TRACKING >> +static inline struct pfnmap_track_ctx *pfnmap_track_ctx_alloc(unsigned long pfn, >> + unsigned long size, pgprot_t *prot) >> +{ >> + struct pfnmap_track_ctx *ctx; >> + >> + if (pfnmap_track(pfn, size, prot)) >> + return ERR_PTR(-EINVAL); >> + >> + ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); >> + if (unlikely(!ctx)) { >> + pfnmap_untrack(pfn, size); >> + return ERR_PTR(-ENOMEM); >> + } >> + >> + ctx->pfn = pfn; >> + ctx->size = size; >> + kref_init(&ctx->kref); >> + return ctx; >> +} >> + >> +void pfnmap_track_ctx_release(struct kref *ref) >> +{ >> + struct pfnmap_track_ctx *ctx = container_of(ref, struct pfnmap_track_ctx, kref); >> + >> + pfnmap_untrack(ctx->pfn, ctx->size); >> + kfree(ctx); >> +} >> +#endif /* __HAVE_PFNMAP_TRACKING */ >> + >> /** >> * remap_pfn_range - remap kernel memory to userspace >> * @vma: user vma to map to >> @@ -2884,20 +2903,51 @@ int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr, >> * >> * Return: %0 on success, negative error code otherwise. >> */ >> +#ifdef __HAVE_PFNMAP_TRACKING >> int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr, >> unsigned long pfn, unsigned long size, pgprot_t prot) >> { >> + struct pfnmap_track_ctx *ctx = NULL; >> int err; >> >> - err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size)); >> - if (err) >> + size = PAGE_ALIGN(size); >> + >> + /* >> + * If we cover the full VMA, we'll perform actual tracking, and >> + * remember to untrack when the last reference to our tracking >> + * context from a VMA goes away. We'll keep tracking the whole pfn >> + * range even during VMA splits and partial unmapping. >> + * >> + * If we only cover parts of the VMA, we'll only setup the cachemode >> + * in the pgprot for the pfn range. >> + */ >> + if (addr == vma->vm_start && addr + size == vma->vm_end) { >> + if (vma->pfnmap_track_ctx) >> + return -EINVAL; >> + ctx = pfnmap_track_ctx_alloc(pfn, size, &prot); >> + if (IS_ERR(ctx)) >> + return PTR_ERR(ctx); >> + } else if (pfnmap_setup_cachemode(pfn, size, &prot)) { >> return -EINVAL; >> + } >> >> err = remap_pfn_range_notrack(vma, addr, pfn, size, prot); >> - if (err) >> - untrack_pfn(vma, pfn, PAGE_ALIGN(size), true); >> + if (ctx) { >> + if (err) >> + kref_put(&ctx->kref, pfnmap_track_ctx_release); >> + else >> + vma->pfnmap_track_ctx = ctx; >> + } >> return err; >> } >> + >> +#else >> +int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr, >> + unsigned long pfn, unsigned long size, pgprot_t prot) >> +{ >> + return remap_pfn_range_notrack(vma, addr, pfn, size, prot); >> +} >> +#endif >> EXPORT_SYMBOL(remap_pfn_range); >> >> /** >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 50f902c08341a..09c563c951123 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -1784,11 +1784,6 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) >> tmp = vm_area_dup(mpnt); >> if (!tmp) >> goto fail_nomem; >> - >> - /* track_pfn_copy() will later take care of copying internal state. */ >> - if (unlikely(tmp->vm_flags & VM_PFNMAP)) >> - untrack_pfn_clear(tmp); >> - >> retval = vma_dup_policy(mpnt, tmp); >> if (retval) >> goto fail_nomem_policy; >> diff --git a/mm/mremap.c b/mm/mremap.c >> index 7db9da609c84f..6e78e02f74bd3 100644 >> --- a/mm/mremap.c >> +++ b/mm/mremap.c >> @@ -1191,10 +1191,6 @@ static int copy_vma_and_data(struct vma_remap_struct *vrm, >> if (is_vm_hugetlb_page(vma)) >> clear_vma_resv_huge_pages(vma); >> >> - /* Tell pfnmap has moved from this vma */ >> - if (unlikely(vma->vm_flags & VM_PFNMAP)) >> - untrack_pfn_clear(vma); >> - >> *new_vma_ptr = new_vma; >> return err; >> } >> diff --git a/mm/vma_init.c b/mm/vma_init.c >> index 967ca85179864..8e53c7943561e 100644 >> --- a/mm/vma_init.c >> +++ b/mm/vma_init.c >> @@ -71,7 +71,51 @@ static void vm_area_init_from(const struct vm_area_struct *src, >> #ifdef CONFIG_NUMA >> dest->vm_policy = src->vm_policy; >> #endif >> +#ifdef __HAVE_PFNMAP_TRACKING >> + dest->pfnmap_track_ctx = NULL; >> +#endif >> +} >> + >> +#ifdef __HAVE_PFNMAP_TRACKING >> +static inline int vma_pfnmap_track_ctx_dup(struct vm_area_struct *orig, >> + struct vm_area_struct *new) >> +{ >> + struct pfnmap_track_ctx *ctx = orig->pfnmap_track_ctx; >> + >> + if (likely(!ctx)) >> + return 0; >> + >> + /* >> + * We don't expect to ever hit this. If ever required, we would have >> + * to duplicate the tracking. >> + */ >> + if (unlikely(kref_read(&ctx->kref) >= REFCOUNT_MAX)) > > How not expected is this? :) maybe use WARN_ON_ONCE() if it really should > never happen? I guess if we mmap a large PFNMAP and then split it into individual PTE-sized chunks, we could get many VMAs per-process referencing that tracing. Combine that with fork() and I assume one could hit this -- when really trying hard to achieve it. (probably as privileged user to get a big VM_PFNMAP, though, but not sure) In that case, a WARN_ON_ONCE() would be bad -- because it could be triggered by the user. We could do a pr_warn_once() instead, stating that this is not supported right now? -- Cheers, David / dhildenb