[PATCH v5 17/25] arm64/mm: ptep_get(): New layer to manage contig bit

Ryan Roberts
2024-02-02T08:09:21Z

Create a new layer for the in-table PTE manipulation APIs. For now, The
existing API is prefixed with double underscore to become the
arch-private API and the public API is just a simple wrapper that calls
the private API.

The public API implementation will subsequently be used to transparently
manipulate the contiguous bit where appropriate. But since there are
already some contig-aware users (e.g. hugetlb, kernel mapper), we must
first ensure those users use the private API directly so that the future
contig-bit manipulations in the public API do not interfere with those
existing uses.

arm64 did not previously define an arch-specific ptep_get(), so override
the default version in the arch code, and also define the private
__ptep_get() version. Currently they both do the same thing that the
default version does (READ_ONCE()). Some arch users (hugetlb) were
already using ptep_get() so convert those to the private API. While
other callsites were doing direct READ_ONCE(), so convert those to use
the appropriate (public/private) API too.

Tested-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
---
arch/arm64/include/asm/pgtable.h | 12 +++++++++---
arch/arm64/kernel/efi.c | 2 +-
arch/arm64/mm/fault.c | 4 ++--
arch/arm64/mm/hugetlbpage.c | 18 +++++++++---------
arch/arm64/mm/kasan_init.c | 2 +-
arch/arm64/mm/mmu.c | 12 ++++++------
arch/arm64/mm/pageattr.c | 4 ++--
arch/arm64/mm/trans_pgd.c | 2 +-
8 files changed, 31 insertions(+), 25 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index fe27a3175618..7dc6b68ee516 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -276,6 +276,11 @@ static inline void __set_pte(pte_t *ptep, pte_t pte)
}
}

+static inline pte_t __ptep_get(pte_t *ptep)
+{
+ return READ_ONCE(*ptep);
+}
+
extern void __sync_icache_dcache(pte_t pteval);
bool pgattr_change_is_safe(u64 old, u64 new);

@@ -303,7 +308,7 @@ static inline void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep,
if (!IS_ENABLED(CONFIG_DEBUG_VM))
return;

- old_pte = READ_ONCE(*ptep);
+ old_pte = __ptep_get(ptep);

if (!pte_valid(old_pte) || !pte_valid(pte))
return;
@@ -905,7 +910,7 @@ static inline int __ptep_test_and_clear_young(struct vm_area_struct *vma,
{
pte_t old_pte, pte;

- pte = READ_ONCE(*ptep);
+ pte = __ptep_get(ptep);
do {
old_pte = pte;
pte = pte_mkold(pte);
@@ -978,7 +983,7 @@ static inline void __ptep_set_wrprotect(struct mm_struct *mm,
{
pte_t old_pte, pte;

- pte = READ_ONCE(*ptep);
+ pte = __ptep_get(ptep);
do {
old_pte = pte;
pte = pte_wrprotect(pte);
@@ -1130,6 +1135,7 @@ void vmemmap_update_pte(unsigned long addr, pte_t *ptep, pte_t pte);
#define vmemmap_update_pte vmemmap_update_pte
#endif

+#define ptep_get __ptep_get
#define set_pte __set_pte
#define set_ptes __set_ptes
#define pte_clear __pte_clear
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 44288a12fc6c..9afcc690fe73 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -103,7 +103,7 @@ static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
{
struct set_perm_data *spd = data;
const efi_memory_desc_t *md = spd->md;
- pte_t pte = READ_ONCE(*ptep);
+ pte_t pte = __ptep_get(ptep);

if (md->attribute & EFI_MEMORY_RO)
pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index dbbc06cfb848..892e8cc8983f 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -191,7 +191,7 @@ static void show_pte(unsigned long addr)
if (!ptep)
break;

- pte = READ_ONCE(*ptep);
+ pte = __ptep_get(ptep);
pr_cont(", pte=%016llx", pte_val(pte));
pte_unmap(ptep);
} while(0);
@@ -214,7 +214,7 @@ int __ptep_set_access_flags(struct vm_area_struct *vma,
pte_t entry, int dirty)
{
pteval_t old_pteval, pteval;
- pte_t pte = READ_ONCE(*ptep);
+ pte_t pte = __ptep_get(ptep);

if (pte_same(pte, entry))
return 0;
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 9949b80baac8..c3db949560f9 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -152,14 +152,14 @@ pte_t huge_ptep_get(pte_t *ptep)
{
int ncontig, i;
size_t pgsize;
- pte_t orig_pte = ptep_get(ptep);
+ pte_t orig_pte = __ptep_get(ptep);

if (!pte_present(orig_pte) || !pte_cont(orig_pte))
return orig_pte;

ncontig = num_contig_ptes(page_size(pte_page(orig_pte)), &pgsize);
for (i = 0; i < ncontig; i++, ptep++) {
- pte_t pte = ptep_get(ptep);
+ pte_t pte = __ptep_get(ptep);

if (pte_dirty(pte))
orig_pte = pte_mkdirty(orig_pte);
@@ -184,7 +184,7 @@ static pte_t get_clear_contig(struct mm_struct *mm,
unsigned long pgsize,
unsigned long ncontig)
{
- pte_t orig_pte = ptep_get(ptep);
+ pte_t orig_pte = __ptep_get(ptep);
unsigned long i;

for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {
@@ -408,7 +408,7 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
{
int ncontig;
size_t pgsize;
- pte_t orig_pte = ptep_get(ptep);
+ pte_t orig_pte = __ptep_get(ptep);

if (!pte_cont(orig_pte))
return __ptep_get_and_clear(mm, addr, ptep);
@@ -431,11 +431,11 @@ static int __cont_access_flags_changed(pte_t *ptep, pte_t pte, int ncontig)
{
int i;

- if (pte_write(pte) != pte_write(ptep_get(ptep)))
+ if (pte_write(pte) != pte_write(__ptep_get(ptep)))
return 1;

for (i = 0; i < ncontig; i++) {
- pte_t orig_pte = ptep_get(ptep + i);
+ pte_t orig_pte = __ptep_get(ptep + i);

if (pte_dirty(pte) != pte_dirty(orig_pte))
return 1;
@@ -492,7 +492,7 @@ void huge_ptep_set_wrprotect(struct mm_struct *mm,
size_t pgsize;
pte_t pte;

- if (!pte_cont(READ_ONCE(*ptep))) {
+ if (!pte_cont(__ptep_get(ptep))) {
__ptep_set_wrprotect(mm, addr, ptep);
return;
}
@@ -517,7 +517,7 @@ pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
size_t pgsize;
int ncontig;

- if (!pte_cont(READ_ONCE(*ptep)))
+ if (!pte_cont(__ptep_get(ptep)))
return ptep_clear_flush(vma, addr, ptep);

ncontig = find_num_contig(mm, addr, ptep, &pgsize);
@@ -550,7 +550,7 @@ pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr
* when the permission changes from executable to non-executable
* in cases where cpu is affected with errata #2645198.
*/
- if (pte_user_exec(READ_ONCE(*ptep)))
+ if (pte_user_exec(__ptep_get(ptep)))
return huge_ptep_clear_flush(vma, addr, ptep);
}
return huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index f659bd98c63f..9ee16cfce587 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -113,7 +113,7 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE);
next = addr + PAGE_SIZE;
__set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
- } while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)));
+ } while (ptep++, addr = next, addr != end && pte_none(__ptep_get(ptep)));
}

static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index bcaa5a5d86f8..8c1ab90bb1e5 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -173,7 +173,7 @@ static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end,

ptep = pte_set_fixmap_offset(pmdp, addr);
do {
- pte_t old_pte = READ_ONCE(*ptep);
+ pte_t old_pte = __ptep_get(ptep);

__set_pte(ptep, pfn_pte(__phys_to_pfn(phys), prot));

@@ -182,7 +182,7 @@ static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end,
* only allow updates to the permission attributes.
*/
BUG_ON(!pgattr_change_is_safe(pte_val(old_pte),
- READ_ONCE(pte_val(*ptep))));
+ pte_val(__ptep_get(ptep))));

phys += PAGE_SIZE;
} while (ptep++, addr += PAGE_SIZE, addr != end);
@@ -854,7 +854,7 @@ static void unmap_hotplug_pte_range(pmd_t *pmdp, unsigned long addr,

do {
ptep = pte_offset_kernel(pmdp, addr);
- pte = READ_ONCE(*ptep);
+ pte = __ptep_get(ptep);
if (pte_none(pte))
continue;

@@ -987,7 +987,7 @@ static void free_empty_pte_table(pmd_t *pmdp, unsigned long addr,

do {
ptep = pte_offset_kernel(pmdp, addr);
- pte = READ_ONCE(*ptep);
+ pte = __ptep_get(ptep);

/*
* This is just a sanity check here which verifies that
@@ -1006,7 +1006,7 @@ static void free_empty_pte_table(pmd_t *pmdp, unsigned long addr,
*/
ptep = pte_offset_kernel(pmdp, 0UL);
for (i = 0; i < PTRS_PER_PTE; i++) {
- if (!pte_none(READ_ONCE(ptep[i])))
+ if (!pte_none(__ptep_get(&ptep[i])))
return;
}

@@ -1503,7 +1503,7 @@ pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, pte
* when the permission changes from executable to non-executable
* in cases where cpu is affected with errata #2645198.
*/
- if (pte_user_exec(READ_ONCE(*ptep)))
+ if (pte_user_exec(ptep_get(ptep)))
return ptep_clear_flush(vma, addr, ptep);
}
return ptep_get_and_clear(vma->vm_mm, addr, ptep);
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index a7996d8edf0a..0c4e3ecf989d 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -36,7 +36,7 @@ bool can_set_direct_map(void)
static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
{
struct page_change_data *cdata = data;
- pte_t pte = READ_ONCE(*ptep);
+ pte_t pte = __ptep_get(ptep);

pte = clear_pte_bit(pte, cdata->clear_mask);
pte = set_pte_bit(pte, cdata->set_mask);
@@ -245,5 +245,5 @@ bool kernel_page_present(struct page *page)
return true;

ptep = pte_offset_kernel(pmdp, addr);
- return pte_valid(READ_ONCE(*ptep));
+ return pte_valid(__ptep_get(ptep));
}
diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
index 230b607cf881..5139a28130c0 100644
--- a/arch/arm64/mm/trans_pgd.c
+++ b/arch/arm64/mm/trans_pgd.c
@@ -33,7 +33,7 @@ static void *trans_alloc(struct trans_pgd_info *info)

static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr)
{
- pte_t pte = READ_ONCE(*src_ptep);
+ pte_t pte = __ptep_get(src_ptep);

if (pte_valid(pte)) {
/*
--
2.25.1