The patch titled
Subject: mm/hmm: remove HMM_PFN_READ flag and ignore peculiar architecture
has been added to the -mm tree. Its filename is
mm-hmm-remove-hmm_pfn_read-flag-and-ignore-peculiar-architecture.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-hmm-remove-hmm_pfn_read-flag-and-ignore-peculiar-architecture.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-hmm-remove-hmm_pfn_read-flag-and-ignore-peculiar-architecture.patch
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------------------------------------------------------
From: Jérôme Glisse <jglisse@xxxxxxxxxx>
Subject: mm/hmm: remove HMM_PFN_READ flag and ignore peculiar architecture
Only peculiar architectures allow write without read thus assume that any
valid pfn do allow for read. Note we do not care for write only because
it does make sense with thing like atomic compare and exchange or any
other operations that allow you to get the memory value through them.
Link: http://lkml.kernel.org/r/20180316191414.3223-7-jglisse@xxxxxxxxxx
Signed-off-by: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: Evgeny Baskakov <ebaskakov@xxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Mark Hairgrove <mhairgrove@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/hmm.h | 14 ++++++--------
mm/hmm.c | 28 ++++++++++++++++++++++++----
2 files changed, 30 insertions(+), 12 deletions(-)
diff -puN include/linux/hmm.h~mm-hmm-remove-hmm_pfn_read-flag-and-ignore-peculiar-architecture include/linux/hmm.h
--- a/include/linux/hmm.h~mm-hmm-remove-hmm_pfn_read-flag-and-ignore-peculiar-architecture
+++ a/include/linux/hmm.h
@@ -84,7 +84,6 @@ struct hmm;
*
* Flags:
* HMM_PFN_VALID: pfn is valid
- * HMM_PFN_READ: CPU page table has read permission set
* HMM_PFN_WRITE: CPU page table has write permission set
* HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory
* HMM_PFN_EMPTY: corresponding CPU page table entry is pte_none()
@@ -97,13 +96,12 @@ struct hmm;
typedef unsigned long hmm_pfn_t;
#define HMM_PFN_VALID (1 << 0)
-#define HMM_PFN_READ (1 << 1)
-#define HMM_PFN_WRITE (1 << 2)
-#define HMM_PFN_ERROR (1 << 3)
-#define HMM_PFN_EMPTY (1 << 4)
-#define HMM_PFN_SPECIAL (1 << 5)
-#define HMM_PFN_DEVICE_UNADDRESSABLE (1 << 6)
-#define HMM_PFN_SHIFT 7
+#define HMM_PFN_WRITE (1 << 1)
+#define HMM_PFN_ERROR (1 << 2)
+#define HMM_PFN_EMPTY (1 << 3)
+#define HMM_PFN_SPECIAL (1 << 4)
+#define HMM_PFN_DEVICE_UNADDRESSABLE (1 << 5)
+#define HMM_PFN_SHIFT 6
/*
* hmm_pfn_t_to_page() - return struct page pointed to by a valid hmm_pfn_t
diff -puN mm/hmm.c~mm-hmm-remove-hmm_pfn_read-flag-and-ignore-peculiar-architecture mm/hmm.c
--- a/mm/hmm.c~mm-hmm-remove-hmm_pfn_read-flag-and-ignore-peculiar-architecture
+++ a/mm/hmm.c
@@ -374,11 +374,9 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
hmm_pfn_t *pfns = range->pfns;
unsigned long addr = start, i;
bool write_fault;
- hmm_pfn_t flag;
pte_t *ptep;
i = (addr - range->start) >> PAGE_SHIFT;
- flag = vma->vm_flags & VM_READ ? HMM_PFN_READ : 0;
write_fault = hmm_vma_walk->fault & hmm_vma_walk->write;
again:
@@ -390,6 +388,7 @@ again:
if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) {
unsigned long pfn;
+ hmm_pfn_t flag = 0;
pmd_t pmd;
/*
@@ -454,7 +453,6 @@ again:
} else if (write_fault)
goto fault;
pfns[i] |= HMM_PFN_DEVICE_UNADDRESSABLE;
- pfns[i] |= flag;
} else if (is_migration_entry(entry)) {
if (hmm_vma_walk->fault) {
pte_unmap(ptep);
@@ -474,7 +472,7 @@ again:
if (write_fault && !pte_write(pte))
goto fault;
- pfns[i] = hmm_pfn_t_from_pfn(pte_pfn(pte)) | flag;
+ pfns[i] = hmm_pfn_t_from_pfn(pte_pfn(pte));
pfns[i] |= pte_write(pte) ? HMM_PFN_WRITE : 0;
continue;
@@ -536,6 +534,17 @@ int hmm_vma_get_pfns(struct hmm_range *r
list_add_rcu(&range->list, &hmm->ranges);
spin_unlock(&hmm->lock);
+ if (!(vma->vm_flags & VM_READ)) {
+ /*
+ * If vma do not allow read assume it does not allow write as
+ * only peculiar architecture allow write without read and this
+ * is not a case we care about (some operation like atomic no
+ * longer make sense).
+ */
+ hmm_pfns_clear(range->pfns, range->start, range->end);
+ return 0;
+ }
+
hmm_vma_walk.fault = false;
hmm_vma_walk.range = range;
mm_walk.private = &hmm_vma_walk;
@@ -690,6 +699,17 @@ int hmm_vma_fault(struct hmm_range *rang
list_add_rcu(&range->list, &hmm->ranges);
spin_unlock(&hmm->lock);
+ if (!(vma->vm_flags & VM_READ)) {
+ /*
+ * If vma do not allow read assume it does not allow write as
+ * only peculiar architecture allow write without read and this
+ * is not a case we care about (some operation like atomic no
+ * longer make sense).
+ */
+ hmm_pfns_clear(range->pfns, range->start, range->end);
+ return 0;
+ }
+
/* FIXME support hugetlb fs */
if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
hmm_pfns_special(range->pfns, range->start, range->end);
_
Patches currently in -mm which might be from jglisse@xxxxxxxxxx are
mm-hmm-fix-header-file-if-else-endif-maze.patch
mm-hmm-hmm_pfns_bad-was-accessing-wrong-struct.patch
mm-hmm-use-struct-for-hmm_vma_fault-hmm_vma_get_pfns-parameters.patch
mm-hmm-remove-hmm_pfn_read-flag-and-ignore-peculiar-architecture.patch
mm-hmm-use-uint64_t-for-hmm-pfn-instead-of-defining-hmm_pfn_t-to-ulong.patch
mm-hmm-cleanup-special-vma-handling-vm_special.patch
mm-hmm-do-not-differentiate-between-empty-entry-or-missing-directory.patch
mm-hmm-rename-hmm_pfn_device_unaddressable-to-hmm_pfn_device_private.patch
mm-hmm-move-hmm_pfns_clear-closer-to-where-it-is-use.patch
mm-hmm-factor-out-pte-and-pmd-handling-to-simplify-hmm_vma_walk_pmd.patch
mm-hmm-change-hmm_vma_fault-to-allow-write-fault-on-page-basis.patch
mm-hmm-use-device-driver-encoding-for-hmm-pfn.patch
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