From: Peter Xu <peterx@redhat.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Axel Rasmussen <axelrasmussen@google.com>,
Nadav Amit <nadav.amit@gmail.com>,
Jerome Glisse <jglisse@redhat.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Jason Gunthorpe <jgg@ziepe.ca>,
Alistair Popple <apopple@nvidia.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
peterx@redhat.com, Andrea Arcangeli <aarcange@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Tiberiu Georgescu <tiberiu.georgescu@nutanix.com>,
Hugh Dickins <hughd@google.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>
Subject: [PATCH v5 21/26] hugetlb/userfaultfd: Handle uffd-wp special pte in hugetlb pf handler
Date: Thu, 15 Jul 2021 16:16:39 -0400 [thread overview]
Message-ID: <20210715201639.211982-1-peterx@redhat.com> (raw)
In-Reply-To: <20210715201422.211004-1-peterx@redhat.com>
Teach the hugetlb page fault code to understand uffd-wp special pte. For
example, when seeing such a pte we need to convert any write fault into a read
one (which is fake - we'll retry the write later if so). Meanwhile, for
handle_userfault() we'll need to make sure we must wait for the special swap
pte too just like a none pte.
Note that we also need to teach UFFDIO_COPY about this special pte across the
code path so that we can safely install a new page at this special pte as long
as we know it's a stall entry.
Signed-off-by: Peter Xu <peterx@redhat.com>
---
fs/userfaultfd.c | 5 ++++-
mm/hugetlb.c | 26 ++++++++++++++++++++------
mm/userfaultfd.c | 5 ++++-
3 files changed, 28 insertions(+), 8 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index e1c1cbc7bcc8..644df737fbb2 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -245,8 +245,11 @@ static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
/*
* Lockless access: we're in a wait_event so it's ok if it
* changes under us.
+ *
+ * Regarding uffd-wp special case, please refer to comments in
+ * userfaultfd_must_wait().
*/
- if (huge_pte_none(pte))
+ if (huge_pte_none(pte) || pte_swp_uffd_wp_special(pte))
ret = true;
if (!huge_pte_write(pte) && (reason & VM_UFFD_WP))
ret = true;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 517ee30f272c..5941b5cd7ecc 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4786,7 +4786,8 @@ static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma,
static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
struct vm_area_struct *vma,
struct address_space *mapping, pgoff_t idx,
- unsigned long address, pte_t *ptep, unsigned int flags)
+ unsigned long address, pte_t *ptep,
+ pte_t old_pte, unsigned int flags)
{
struct hstate *h = hstate_vma(vma);
vm_fault_t ret = VM_FAULT_SIGBUS;
@@ -4910,7 +4911,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
ptl = huge_pte_lock(h, mm, ptep);
ret = 0;
- if (!huge_pte_none(huge_ptep_get(ptep)))
+ if (!pte_same(huge_ptep_get(ptep), old_pte))
goto backout;
if (anon_rmap) {
@@ -4920,6 +4921,12 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
page_dup_rmap(page, true);
new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
&& (vma->vm_flags & VM_SHARED)));
+ /*
+ * If this pte was previously wr-protected, keep it wr-protected even
+ * if populated.
+ */
+ if (unlikely(pte_swp_uffd_wp_special(old_pte)))
+ new_pte = huge_pte_wrprotect(huge_pte_mkuffd_wp(new_pte));
set_huge_pte_at(mm, haddr, ptep, new_pte);
hugetlb_count_add(pages_per_huge_page(h), mm);
@@ -5035,8 +5042,13 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
mutex_lock(&hugetlb_fault_mutex_table[hash]);
entry = huge_ptep_get(ptep);
- if (huge_pte_none(entry)) {
- ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep, flags);
+ /*
+ * uffd-wp-special should be handled merely the same as pte none
+ * because it's basically a none pte with a special marker
+ */
+ if (huge_pte_none(entry) || pte_swp_uffd_wp_special(entry)) {
+ ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep,
+ entry, flags);
goto out_mutex;
}
@@ -5170,7 +5182,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr);
unsigned long size;
int vm_shared = dst_vma->vm_flags & VM_SHARED;
- pte_t _dst_pte;
+ pte_t _dst_pte, cur_pte;
spinlock_t *ptl;
int ret = -ENOMEM;
struct page *page;
@@ -5287,8 +5299,10 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
if (idx >= size)
goto out_release_unlock;
+ cur_pte = huge_ptep_get(dst_pte);
ret = -EEXIST;
- if (!huge_pte_none(huge_ptep_get(dst_pte)))
+ /* Please refer to shmem_mfill_atomic_pte() for uffd-wp special case */
+ if (!huge_pte_none(cur_pte) && !pte_swp_uffd_wp_special(cur_pte))
goto out_release_unlock;
if (vm_shared) {
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 7ba721aca1c5..a8038903effd 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -363,6 +363,8 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
}
while (src_addr < src_start + len) {
+ pte_t pteval;
+
BUG_ON(dst_addr >= dst_start + len);
/*
@@ -385,8 +387,9 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
goto out_unlock;
}
+ pteval = huge_ptep_get(dst_pte);
if (mode != MCOPY_ATOMIC_CONTINUE &&
- !huge_pte_none(huge_ptep_get(dst_pte))) {
+ !huge_pte_none(pteval) && !pte_swp_uffd_wp_special(pteval)) {
err = -EEXIST;
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
i_mmap_unlock_read(mapping);
--
2.31.1
next prev parent reply other threads:[~2021-07-15 20:16 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-15 20:13 [PATCH v5 00/26] userfaultfd-wp: Support shmem and hugetlbfs Peter Xu
2021-07-15 20:13 ` [PATCH v5 01/26] mm/shmem: Unconditionally set pte dirty in mfill_atomic_install_pte Peter Xu
2021-07-15 20:13 ` [PATCH v5 02/26] shmem/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-07-15 20:13 ` [PATCH v5 03/26] mm: Clear vmf->pte after pte_unmap_same() returns Peter Xu
2021-07-15 20:14 ` [PATCH v5 04/26] mm/userfaultfd: Introduce special pte for unmapped file-backed mem Peter Xu
2021-07-15 20:14 ` [PATCH v5 05/26] mm/swap: Introduce the idea of special swap ptes Peter Xu
2021-07-16 5:50 ` Alistair Popple
2021-07-16 19:11 ` Peter Xu
2021-07-21 11:28 ` Alistair Popple
2021-07-21 21:35 ` Peter Xu
2021-07-22 1:08 ` Alistair Popple
2021-07-22 15:21 ` Peter Xu
2021-07-15 20:14 ` [PATCH v5 06/26] shmem/userfaultfd: Handle uffd-wp special pte in page fault handler Peter Xu
2021-07-15 20:14 ` [PATCH v5 07/26] mm: Drop first_index/last_index in zap_details Peter Xu
2021-07-15 20:14 ` [PATCH v5 08/26] mm: Introduce zap_details.zap_flags Peter Xu
2021-07-15 20:14 ` [PATCH v5 09/26] mm: Introduce ZAP_FLAG_SKIP_SWAP Peter Xu
2021-07-15 20:14 ` [PATCH v5 10/26] shmem/userfaultfd: Persist uffd-wp bit across zapping for file-backed Peter Xu
2021-07-15 20:15 ` [PATCH v5 11/26] shmem/userfaultfd: Allow wr-protect none pte for file-backed mem Peter Xu
2021-07-15 20:16 ` [PATCH v5 12/26] shmem/userfaultfd: Allows file-back mem to be uffd wr-protected on thps Peter Xu
2021-07-15 20:16 ` [PATCH v5 13/26] shmem/userfaultfd: Handle the left-overed special swap ptes Peter Xu
2021-07-15 20:16 ` [PATCH v5 14/26] shmem/userfaultfd: Pass over uffd-wp special swap pte when fork() Peter Xu
2021-07-15 20:16 ` [PATCH v5 15/26] mm/hugetlb: Drop __unmap_hugepage_range definition from hugetlb.h Peter Xu
2021-07-15 20:16 ` [PATCH v5 16/26] mm/hugetlb: Introduce huge pte version of uffd-wp helpers Peter Xu
2021-07-15 20:16 ` [PATCH v5 17/26] hugetlb/userfaultfd: Hook page faults for uffd write protection Peter Xu
2021-07-20 15:37 ` kernel test robot
2021-07-21 21:50 ` Peter Xu
2021-07-15 20:16 ` [PATCH v5 18/26] hugetlb/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-07-20 23:59 ` kernel test robot
2021-07-15 20:16 ` [PATCH v5 19/26] hugetlb/userfaultfd: Handle UFFDIO_WRITEPROTECT Peter Xu
2021-07-21 8:24 ` kernel test robot
2021-07-15 20:16 ` [PATCH v5 20/26] mm/hugetlb: Introduce huge version of special swap pte helpers Peter Xu
2021-07-15 20:16 ` Peter Xu [this message]
2021-07-15 20:16 ` [PATCH v5 22/26] hugetlb/userfaultfd: Allow wr-protect none ptes Peter Xu
2021-07-15 20:16 ` [PATCH v5 23/26] hugetlb/userfaultfd: Only drop uffd-wp special pte if required Peter Xu
2021-07-15 20:16 ` [PATCH v5 24/26] mm/pagemap: Recognize uffd-wp bit for shmem/hugetlbfs Peter Xu
2021-07-19 9:53 ` Tiberiu Georgescu
2021-07-19 16:03 ` Peter Xu
2021-07-19 17:23 ` Tiberiu Georgescu
2021-07-19 17:56 ` Peter Xu
2021-07-21 14:38 ` Ivan Teterevkov
2021-07-21 16:19 ` David Hildenbrand
2021-07-21 19:54 ` Ivan Teterevkov
2021-07-21 22:28 ` Peter Xu
2021-07-21 22:57 ` Peter Xu
2021-07-22 6:27 ` David Hildenbrand
2021-07-22 16:08 ` Peter Xu
2021-07-15 20:16 ` [PATCH v5 25/26] mm/userfaultfd: Enable write protection for shmem & hugetlbfs Peter Xu
2021-07-15 20:16 ` [PATCH v5 26/26] userfaultfd/selftests: Enable uffd-wp for shmem/hugetlbfs Peter Xu
2021-07-19 19:21 ` [PATCH v5 00/26] userfaultfd-wp: Support shmem and hugetlbfs David Hildenbrand
2021-07-19 20:12 ` Peter Xu
2021-07-22 18:30 ` Peter Xu
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