diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/hmm.c | 5 | ||||
| -rw-r--r-- | mm/memory.c | 127 | ||||
| -rw-r--r-- | mm/mprotect.c | 8 | ||||
| -rw-r--r-- | mm/page_vma_mapped.c | 9 | ||||
| -rw-r--r-- | mm/rmap.c | 186 |
5 files changed, 328 insertions, 7 deletions
@@ -26,6 +26,8 @@ #include <linux/mmu_notifier.h> #include <linux/memory_hotplug.h> +#include "internal.h" + struct hmm_vma_walk { struct hmm_range *range; unsigned long last; @@ -271,6 +273,9 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, if (!non_swap_entry(entry)) goto fault; + if (is_device_exclusive_entry(entry)) + goto fault; + if (is_migration_entry(entry)) { pte_unmap(ptep); hmm_vma_walk->last = addr; diff --git a/mm/memory.c b/mm/memory.c index 75feddbf0190..747a01d495f2 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -699,6 +699,68 @@ out: } #endif +static void restore_exclusive_pte(struct vm_area_struct *vma, + struct page *page, unsigned long address, + pte_t *ptep) +{ + pte_t pte; + swp_entry_t entry; + + pte = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot))); + if (pte_swp_soft_dirty(*ptep)) + pte = pte_mksoft_dirty(pte); + + entry = pte_to_swp_entry(*ptep); + if (pte_swp_uffd_wp(*ptep)) + pte = pte_mkuffd_wp(pte); + else if (is_writable_device_exclusive_entry(entry)) + pte = maybe_mkwrite(pte_mkdirty(pte), vma); + + set_pte_at(vma->vm_mm, address, ptep, pte); + + /* + * No need to take a page reference as one was already + * created when the swap entry was made. + */ + if (PageAnon(page)) + page_add_anon_rmap(page, vma, address, false); + else + /* + * Currently device exclusive access only supports anonymous + * memory so the entry shouldn't point to a filebacked page. + */ + WARN_ON_ONCE(!PageAnon(page)); + + if (vma->vm_flags & VM_LOCKED) + mlock_vma_page(page); + + /* + * No need to invalidate - it was non-present before. However + * secondary CPUs may have mappings that need invalidating. + */ + update_mmu_cache(vma, address, ptep); +} + +/* + * Tries to restore an exclusive pte if the page lock can be acquired without + * sleeping. + */ +static int +try_restore_exclusive_pte(pte_t *src_pte, struct vm_area_struct *vma, + unsigned long addr) +{ + swp_entry_t entry = pte_to_swp_entry(*src_pte); + struct page *page = pfn_swap_entry_to_page(entry); + + if (trylock_page(page)) { + restore_exclusive_pte(vma, page, addr, src_pte); + unlock_page(page); + return 0; + } + + return -EBUSY; +} + /* * copy one vm_area from one task to the other. Assumes the page tables * already present in the new task to be cleared in the whole range @@ -780,6 +842,17 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, pte = pte_swp_mkuffd_wp(pte); set_pte_at(src_mm, addr, src_pte, pte); } + } else if (is_device_exclusive_entry(entry)) { + /* + * Make device exclusive entries present by restoring the + * original entry then copying as for a present pte. Device + * exclusive entries currently only support private writable + * (ie. COW) mappings. + */ + VM_BUG_ON(!is_cow_mapping(src_vma->vm_flags)); + if (try_restore_exclusive_pte(src_pte, src_vma, addr)) + return -EBUSY; + return -ENOENT; } if (!userfaultfd_wp(dst_vma)) pte = pte_swp_clear_uffd_wp(pte); @@ -980,9 +1053,18 @@ again: if (ret == -EIO) { entry = pte_to_swp_entry(*src_pte); break; + } else if (ret == -EBUSY) { + break; + } else if (!ret) { + progress += 8; + continue; } - progress += 8; - continue; + + /* + * Device exclusive entry restored, continue by copying + * the now present pte. + */ + WARN_ON_ONCE(ret != -ENOENT); } /* copy_present_pte() will clear `*prealloc' if consumed */ ret = copy_present_pte(dst_vma, src_vma, dst_pte, src_pte, @@ -1020,6 +1102,8 @@ again: goto out; } entry.val = 0; + } else if (ret == -EBUSY) { + goto out; } else if (ret == -EAGAIN) { prealloc = page_copy_prealloc(src_mm, src_vma, addr); if (!prealloc) @@ -1287,7 +1371,8 @@ again: } entry = pte_to_swp_entry(ptent); - if (is_device_private_entry(entry)) { + if (is_device_private_entry(entry) || + is_device_exclusive_entry(entry)) { struct page *page = pfn_swap_entry_to_page(entry); if (unlikely(details && details->check_mapping)) { @@ -1303,7 +1388,10 @@ again: pte_clear_not_present_full(mm, addr, pte, tlb->fullmm); rss[mm_counter(page)]--; - page_remove_rmap(page, false); + + if (is_device_private_entry(entry)) + page_remove_rmap(page, false); + put_page(page); continue; } @@ -3352,6 +3440,34 @@ void unmap_mapping_range(struct address_space *mapping, EXPORT_SYMBOL(unmap_mapping_range); /* + * Restore a potential device exclusive pte to a working pte entry + */ +static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf) +{ + struct page *page = vmf->page; + struct vm_area_struct *vma = vmf->vma; + struct mmu_notifier_range range; + + if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) + return VM_FAULT_RETRY; + mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, vma, + vma->vm_mm, vmf->address & PAGE_MASK, + (vmf->address & PAGE_MASK) + PAGE_SIZE, NULL); + mmu_notifier_invalidate_range_start(&range); + + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, + &vmf->ptl); + if (likely(pte_same(*vmf->pte, vmf->orig_pte))) + restore_exclusive_pte(vma, page, vmf->address, vmf->pte); + + pte_unmap_unlock(vmf->pte, vmf->ptl); + unlock_page(page); + + mmu_notifier_invalidate_range_end(&range); + return 0; +} + +/* * We enter with non-exclusive mmap_lock (to exclude vma changes, * but allow concurrent faults), and pte mapped but not yet locked. * We return with pte unmapped and unlocked. @@ -3379,6 +3495,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) if (is_migration_entry(entry)) { migration_entry_wait(vma->vm_mm, vmf->pmd, vmf->address); + } else if (is_device_exclusive_entry(entry)) { + vmf->page = pfn_swap_entry_to_page(entry); + ret = remove_device_exclusive_entry(vmf); } else if (is_device_private_entry(entry)) { vmf->page = pfn_swap_entry_to_page(entry); ret = vmf->page->pgmap->ops->migrate_to_ram(vmf); diff --git a/mm/mprotect.c b/mm/mprotect.c index ee5961888e70..883e2cc85cad 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -165,6 +165,14 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, newpte = swp_entry_to_pte(entry); if (pte_swp_uffd_wp(oldpte)) newpte = pte_swp_mkuffd_wp(newpte); + } else if (is_writable_device_exclusive_entry(entry)) { + entry = make_readable_device_exclusive_entry( + swp_offset(entry)); + newpte = swp_entry_to_pte(entry); + if (pte_swp_soft_dirty(oldpte)) + newpte = pte_swp_mksoft_dirty(newpte); + if (pte_swp_uffd_wp(oldpte)) + newpte = pte_swp_mkuffd_wp(newpte); } else { newpte = oldpte; } diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c index 4df6093e759b..f7b331081791 100644 --- a/mm/page_vma_mapped.c +++ b/mm/page_vma_mapped.c @@ -41,7 +41,8 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw) /* Handle un-addressable ZONE_DEVICE memory */ entry = pte_to_swp_entry(*pvmw->pte); - if (!is_device_private_entry(entry)) + if (!is_device_private_entry(entry) && + !is_device_exclusive_entry(entry)) return false; } else if (!pte_present(*pvmw->pte)) return false; @@ -93,7 +94,8 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw) return false; entry = pte_to_swp_entry(*pvmw->pte); - if (!is_migration_entry(entry)) + if (!is_migration_entry(entry) && + !is_device_exclusive_entry(entry)) return false; pfn = swp_offset(entry); @@ -102,7 +104,8 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw) /* Handle un-addressable ZONE_DEVICE memory */ entry = pte_to_swp_entry(*pvmw->pte); - if (!is_device_private_entry(entry)) + if (!is_device_private_entry(entry) && + !is_device_exclusive_entry(entry)) return false; pfn = swp_offset(entry); diff --git a/mm/rmap.c b/mm/rmap.c index b922c7074cdd..37c24672125c 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2028,6 +2028,192 @@ void page_mlock(struct page *page) rmap_walk(page, &rwc); } +#ifdef CONFIG_DEVICE_PRIVATE +struct make_exclusive_args { + struct mm_struct *mm; + unsigned long address; + void *owner; + bool valid; +}; + +static bool page_make_device_exclusive_one(struct page *page, + struct vm_area_struct *vma, unsigned long address, void *priv) +{ + struct mm_struct *mm = vma->vm_mm; + struct page_vma_mapped_walk pvmw = { + .page = page, + .vma = vma, + .address = address, + }; + struct make_exclusive_args *args = priv; + pte_t pteval; + struct page *subpage; + bool ret = true; + struct mmu_notifier_range range; + swp_entry_t entry; + pte_t swp_pte; + + mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, vma, + vma->vm_mm, address, min(vma->vm_end, + address + page_size(page)), args->owner); + mmu_notifier_invalidate_range_start(&range); + + while (page_vma_mapped_walk(&pvmw)) { + /* Unexpected PMD-mapped THP? */ + VM_BUG_ON_PAGE(!pvmw.pte, page); + + if (!pte_present(*pvmw.pte)) { + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + + subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte); + address = pvmw.address; + + /* Nuke the page table entry. */ + flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); + pteval = ptep_clear_flush(vma, address, pvmw.pte); + + /* Move the dirty bit to the page. Now the pte is gone. */ + if (pte_dirty(pteval)) + set_page_dirty(page); + + /* + * Check that our target page is still mapped at the expected + * address. + */ + if (args->mm == mm && args->address == address && + pte_write(pteval)) + args->valid = true; + + /* + * Store the pfn of the page in a special migration + * pte. do_swap_page() will wait until the migration + * pte is removed and then restart fault handling. + */ + if (pte_write(pteval)) + entry = make_writable_device_exclusive_entry( + page_to_pfn(subpage)); + else + entry = make_readable_device_exclusive_entry( + page_to_pfn(subpage)); + swp_pte = swp_entry_to_pte(entry); + if (pte_soft_dirty(pteval)) + swp_pte = pte_swp_mksoft_dirty(swp_pte); + if (pte_uffd_wp(pteval)) + swp_pte = pte_swp_mkuffd_wp(swp_pte); + + set_pte_at(mm, address, pvmw.pte, swp_pte); + + /* + * There is a reference on the page for the swap entry which has + * been removed, so shouldn't take another. + */ + page_remove_rmap(subpage, false); + } + + mmu_notifier_invalidate_range_end(&range); + + return ret; +} + +/** + * page_make_device_exclusive - mark the page exclusively owned by a device + * @page: the page to replace page table entries for + * @mm: the mm_struct where the page is expected to be mapped + * @address: address where the page is expected to be mapped + * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier callbacks + * + * Tries to remove all the page table entries which are mapping this page and + * replace them with special device exclusive swap entries to grant a device + * exclusive access to the page. Caller must hold the page lock. + * + * Returns false if the page is still mapped, or if it could not be unmapped + * from the expected address. Otherwise returns true (success). + */ +static bool page_make_device_exclusive(struct page *page, struct mm_struct *mm, + unsigned long address, void *owner) +{ + struct make_exclusive_args args = { + .mm = mm, + .address = address, + .owner = owner, + .valid = false, + }; + struct rmap_walk_control rwc = { + .rmap_one = page_make_device_exclusive_one, + .done = page_not_mapped, + .anon_lock = page_lock_anon_vma_read, + .arg = &args, + }; + + /* + * Restrict to anonymous pages for now to avoid potential writeback + * issues. Also tail pages shouldn't be passed to rmap_walk so skip + * those. + */ + if (!PageAnon(page) || PageTail(page)) + return false; + + rmap_walk(page, &rwc); + + return args.valid && !page_mapcount(page); +} + +/** + * make_device_exclusive_range() - Mark a range for exclusive use by a device + * @mm: mm_struct of assoicated target process + * @start: start of the region to mark for exclusive device access + * @end: end address of region + * @pages: returns the pages which were successfully marked for exclusive access + * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering + * + * Returns: number of pages found in the range by GUP. A page is marked for + * exclusive access only if the page pointer is non-NULL. + * + * This function finds ptes mapping page(s) to the given address range, locks + * them and replaces mappings with special swap entries preventing userspace CPU + * access. On fault these entries are replaced with the original mapping after + * calling MMU notifiers. + * + * A driver using this to program access from a device must use a mmu notifier + * critical section to hold a device specific lock during programming. Once + * programming is complete it should drop the page lock and reference after + * which point CPU access to the page will revoke the exclusive access. + */ +int make_device_exclusive_range(struct mm_struct *mm, unsigned long start, + unsigned long end, struct page **pages, + void *owner) +{ + long npages = (end - start) >> PAGE_SHIFT; + long i; + + npages = get_user_pages_remote(mm, start, npages, + FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD, + pages, NULL, NULL); + if (npages < 0) + return npages; + + for (i = 0; i < npages; i++, start += PAGE_SIZE) { + if (!trylock_page(pages[i])) { + put_page(pages[i]); + pages[i] = NULL; + continue; + } + + if (!page_make_device_exclusive(pages[i], mm, start, owner)) { + unlock_page(pages[i]); + put_page(pages[i]); + pages[i] = NULL; + } + } + + return npages; +} +EXPORT_SYMBOL_GPL(make_device_exclusive_range); +#endif + void __put_anon_vma(struct anon_vma *anon_vma) { struct anon_vma *root = anon_vma->root; |