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Diffstat (limited to 'arch/s390/mm/pgalloc.c')
-rw-r--r--arch/s390/mm/pgalloc.c244
1 files changed, 176 insertions, 68 deletions
diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c
index 781965f7210e..fd35c1a0213b 100644
--- a/arch/s390/mm/pgalloc.c
+++ b/arch/s390/mm/pgalloc.c
@@ -176,7 +176,75 @@ void page_table_free_pgste(struct page *page)
#endif /* CONFIG_PGSTE */
/*
- * page table entry allocation/free routines.
+ * A 2KB-pgtable is either upper or lower half of a normal page.
+ * The second half of the page may be unused or used as another
+ * 2KB-pgtable.
+ *
+ * Whenever possible the parent page for a new 2KB-pgtable is picked
+ * from the list of partially allocated pages mm_context_t::pgtable_list.
+ * In case the list is empty a new parent page is allocated and added to
+ * the list.
+ *
+ * When a parent page gets fully allocated it contains 2KB-pgtables in both
+ * upper and lower halves and is removed from mm_context_t::pgtable_list.
+ *
+ * When 2KB-pgtable is freed from to fully allocated parent page that
+ * page turns partially allocated and added to mm_context_t::pgtable_list.
+ *
+ * If 2KB-pgtable is freed from the partially allocated parent page that
+ * page turns unused and gets removed from mm_context_t::pgtable_list.
+ * Furthermore, the unused parent page is released.
+ *
+ * As follows from the above, no unallocated or fully allocated parent
+ * pages are contained in mm_context_t::pgtable_list.
+ *
+ * The upper byte (bits 24-31) of the parent page _refcount is used
+ * for tracking contained 2KB-pgtables and has the following format:
+ *
+ * PP AA
+ * 01234567 upper byte (bits 24-31) of struct page::_refcount
+ * || ||
+ * || |+--- upper 2KB-pgtable is allocated
+ * || +---- lower 2KB-pgtable is allocated
+ * |+------- upper 2KB-pgtable is pending for removal
+ * +-------- lower 2KB-pgtable is pending for removal
+ *
+ * (See commit 620b4e903179 ("s390: use _refcount for pgtables") on why
+ * using _refcount is possible).
+ *
+ * When 2KB-pgtable is allocated the corresponding AA bit is set to 1.
+ * The parent page is either:
+ * - added to mm_context_t::pgtable_list in case the second half of the
+ * parent page is still unallocated;
+ * - removed from mm_context_t::pgtable_list in case both hales of the
+ * parent page are allocated;
+ * These operations are protected with mm_context_t::lock.
+ *
+ * When 2KB-pgtable is deallocated the corresponding AA bit is set to 0
+ * and the corresponding PP bit is set to 1 in a single atomic operation.
+ * Thus, PP and AA bits corresponding to the same 2KB-pgtable are mutually
+ * exclusive and may never be both set to 1!
+ * The parent page is either:
+ * - added to mm_context_t::pgtable_list in case the second half of the
+ * parent page is still allocated;
+ * - removed from mm_context_t::pgtable_list in case the second half of
+ * the parent page is unallocated;
+ * These operations are protected with mm_context_t::lock.
+ *
+ * It is important to understand that mm_context_t::lock only protects
+ * mm_context_t::pgtable_list and AA bits, but not the parent page itself
+ * and PP bits.
+ *
+ * Releasing the parent page happens whenever the PP bit turns from 1 to 0,
+ * while both AA bits and the second PP bit are already unset. Then the
+ * parent page does not contain any 2KB-pgtable fragment anymore, and it has
+ * also been removed from mm_context_t::pgtable_list. It is safe to release
+ * the page therefore.
+ *
+ * PGSTE memory spaces use full 4KB-pgtables and do not need most of the
+ * logic described above. Both AA bits are set to 1 to denote a 4KB-pgtable
+ * while the PP bits are never used, nor such a page is added to or removed
+ * from mm_context_t::pgtable_list.
*/
unsigned long *page_table_alloc(struct mm_struct *mm)
{
@@ -192,14 +260,23 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
page = list_first_entry(&mm->context.pgtable_list,
struct page, lru);
mask = atomic_read(&page->_refcount) >> 24;
- mask = (mask | (mask >> 4)) & 3;
- if (mask != 3) {
+ /*
+ * The pending removal bits must also be checked.
+ * Failure to do so might lead to an impossible
+ * value of (i.e 0x13 or 0x23) written to _refcount.
+ * Such values violate the assumption that pending and
+ * allocation bits are mutually exclusive, and the rest
+ * of the code unrails as result. That could lead to
+ * a whole bunch of races and corruptions.
+ */
+ mask = (mask | (mask >> 4)) & 0x03U;
+ if (mask != 0x03U) {
table = (unsigned long *) page_to_virt(page);
bit = mask & 1; /* =1 -> second 2K */
if (bit)
table += PTRS_PER_PTE;
atomic_xor_bits(&page->_refcount,
- 1U << (bit + 24));
+ 0x01U << (bit + 24));
list_del(&page->lru);
}
}
@@ -220,12 +297,12 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
table = (unsigned long *) page_to_virt(page);
if (mm_alloc_pgste(mm)) {
/* Return 4K page table with PGSTEs */
- atomic_xor_bits(&page->_refcount, 3 << 24);
+ atomic_xor_bits(&page->_refcount, 0x03U << 24);
memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
} else {
/* Return the first 2K fragment of the page */
- atomic_xor_bits(&page->_refcount, 1 << 24);
+ atomic_xor_bits(&page->_refcount, 0x01U << 24);
memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE);
spin_lock_bh(&mm->context.lock);
list_add(&page->lru, &mm->context.pgtable_list);
@@ -234,29 +311,53 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
return table;
}
+static void page_table_release_check(struct page *page, void *table,
+ unsigned int half, unsigned int mask)
+{
+ char msg[128];
+
+ if (!IS_ENABLED(CONFIG_DEBUG_VM) || !mask)
+ return;
+ snprintf(msg, sizeof(msg),
+ "Invalid pgtable %p release half 0x%02x mask 0x%02x",
+ table, half, mask);
+ dump_page(page, msg);
+}
+
void page_table_free(struct mm_struct *mm, unsigned long *table)
{
+ unsigned int mask, bit, half;
struct page *page;
- unsigned int bit, mask;
page = virt_to_page(table);
if (!mm_alloc_pgste(mm)) {
/* Free 2K page table fragment of a 4K page */
bit = ((unsigned long) table & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
spin_lock_bh(&mm->context.lock);
- mask = atomic_xor_bits(&page->_refcount, 1U << (bit + 24));
+ /*
+ * Mark the page for delayed release. The actual release
+ * will happen outside of the critical section from this
+ * function or from __tlb_remove_table()
+ */
+ mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
mask >>= 24;
- if (mask & 3)
+ if (mask & 0x03U)
list_add(&page->lru, &mm->context.pgtable_list);
else
list_del(&page->lru);
spin_unlock_bh(&mm->context.lock);
- if (mask != 0)
+ mask = atomic_xor_bits(&page->_refcount, 0x10U << (bit + 24));
+ mask >>= 24;
+ if (mask != 0x00U)
return;
+ half = 0x01U << bit;
} else {
- atomic_xor_bits(&page->_refcount, 3U << 24);
+ half = 0x03U;
+ mask = atomic_xor_bits(&page->_refcount, 0x03U << 24);
+ mask >>= 24;
}
+ page_table_release_check(page, table, half, mask);
pgtable_pte_page_dtor(page);
__free_page(page);
}
@@ -272,47 +373,54 @@ void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
page = virt_to_page(table);
if (mm_alloc_pgste(mm)) {
gmap_unlink(mm, table, vmaddr);
- table = (unsigned long *) ((unsigned long)table | 3);
+ table = (unsigned long *) ((unsigned long)table | 0x03U);
tlb_remove_table(tlb, table);
return;
}
bit = ((unsigned long) table & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
spin_lock_bh(&mm->context.lock);
+ /*
+ * Mark the page for delayed release. The actual release will happen
+ * outside of the critical section from __tlb_remove_table() or from
+ * page_table_free()
+ */
mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
mask >>= 24;
- if (mask & 3)
+ if (mask & 0x03U)
list_add_tail(&page->lru, &mm->context.pgtable_list);
else
list_del(&page->lru);
spin_unlock_bh(&mm->context.lock);
- table = (unsigned long *) ((unsigned long) table | (1U << bit));
+ table = (unsigned long *) ((unsigned long) table | (0x01U << bit));
tlb_remove_table(tlb, table);
}
void __tlb_remove_table(void *_table)
{
- unsigned int mask = (unsigned long) _table & 3;
+ unsigned int mask = (unsigned long) _table & 0x03U, half = mask;
void *table = (void *)((unsigned long) _table ^ mask);
struct page *page = virt_to_page(table);
- switch (mask) {
- case 0: /* pmd, pud, or p4d */
+ switch (half) {
+ case 0x00U: /* pmd, pud, or p4d */
free_pages((unsigned long) table, 2);
- break;
- case 1: /* lower 2K of a 4K page table */
- case 2: /* higher 2K of a 4K page table */
+ return;
+ case 0x01U: /* lower 2K of a 4K page table */
+ case 0x02U: /* higher 2K of a 4K page table */
mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24));
mask >>= 24;
- if (mask != 0)
- break;
- fallthrough;
- case 3: /* 4K page table with pgstes */
- if (mask & 3)
- atomic_xor_bits(&page->_refcount, 3 << 24);
- pgtable_pte_page_dtor(page);
- __free_page(page);
+ if (mask != 0x00U)
+ return;
+ break;
+ case 0x03U: /* 4K page table with pgstes */
+ mask = atomic_xor_bits(&page->_refcount, 0x03U << 24);
+ mask >>= 24;
break;
}
+
+ page_table_release_check(page, table, half, mask);
+ pgtable_pte_page_dtor(page);
+ __free_page(page);
}
/*
@@ -322,34 +430,34 @@ void __tlb_remove_table(void *_table)
static struct kmem_cache *base_pgt_cache;
-static unsigned long base_pgt_alloc(void)
+static unsigned long *base_pgt_alloc(void)
{
- u64 *table;
+ unsigned long *table;
table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
if (table)
- memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
- return (unsigned long) table;
+ memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
+ return table;
}
-static void base_pgt_free(unsigned long table)
+static void base_pgt_free(unsigned long *table)
{
- kmem_cache_free(base_pgt_cache, (void *) table);
+ kmem_cache_free(base_pgt_cache, table);
}
-static unsigned long base_crst_alloc(unsigned long val)
+static unsigned long *base_crst_alloc(unsigned long val)
{
- unsigned long table;
+ unsigned long *table;
- table = __get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
+ table = (unsigned long *)__get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
if (table)
- crst_table_init((unsigned long *)table, val);
+ crst_table_init(table, val);
return table;
}
-static void base_crst_free(unsigned long table)
+static void base_crst_free(unsigned long *table)
{
- free_pages(table, CRST_ALLOC_ORDER);
+ free_pages((unsigned long)table, CRST_ALLOC_ORDER);
}
#define BASE_ADDR_END_FUNC(NAME, SIZE) \
@@ -377,14 +485,14 @@ static inline unsigned long base_lra(unsigned long address)
return real;
}
-static int base_page_walk(unsigned long origin, unsigned long addr,
+static int base_page_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
unsigned long *pte, next;
if (!alloc)
return 0;
- pte = (unsigned long *) origin;
+ pte = origin;
pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
do {
next = base_page_addr_end(addr, end);
@@ -393,13 +501,13 @@ static int base_page_walk(unsigned long origin, unsigned long addr,
return 0;
}
-static int base_segment_walk(unsigned long origin, unsigned long addr,
+static int base_segment_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
- unsigned long *ste, next, table;
+ unsigned long *ste, next, *table;
int rc;
- ste = (unsigned long *) origin;
+ ste = origin;
ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
do {
next = base_segment_addr_end(addr, end);
@@ -409,9 +517,9 @@ static int base_segment_walk(unsigned long origin, unsigned long addr,
table = base_pgt_alloc();
if (!table)
return -ENOMEM;
- *ste = table | _SEGMENT_ENTRY;
+ *ste = __pa(table) | _SEGMENT_ENTRY;
}
- table = *ste & _SEGMENT_ENTRY_ORIGIN;
+ table = __va(*ste & _SEGMENT_ENTRY_ORIGIN);
rc = base_page_walk(table, addr, next, alloc);
if (rc)
return rc;
@@ -422,13 +530,13 @@ static int base_segment_walk(unsigned long origin, unsigned long addr,
return 0;
}
-static int base_region3_walk(unsigned long origin, unsigned long addr,
+static int base_region3_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
- unsigned long *rtte, next, table;
+ unsigned long *rtte, next, *table;
int rc;
- rtte = (unsigned long *) origin;
+ rtte = origin;
rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
do {
next = base_region3_addr_end(addr, end);
@@ -438,9 +546,9 @@ static int base_region3_walk(unsigned long origin, unsigned long addr,
table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
if (!table)
return -ENOMEM;
- *rtte = table | _REGION3_ENTRY;
+ *rtte = __pa(table) | _REGION3_ENTRY;
}
- table = *rtte & _REGION_ENTRY_ORIGIN;
+ table = __va(*rtte & _REGION_ENTRY_ORIGIN);
rc = base_segment_walk(table, addr, next, alloc);
if (rc)
return rc;
@@ -450,13 +558,13 @@ static int base_region3_walk(unsigned long origin, unsigned long addr,
return 0;
}
-static int base_region2_walk(unsigned long origin, unsigned long addr,
+static int base_region2_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
- unsigned long *rste, next, table;
+ unsigned long *rste, next, *table;
int rc;
- rste = (unsigned long *) origin;
+ rste = origin;
rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
do {
next = base_region2_addr_end(addr, end);
@@ -466,9 +574,9 @@ static int base_region2_walk(unsigned long origin, unsigned long addr,
table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
if (!table)
return -ENOMEM;
- *rste = table | _REGION2_ENTRY;
+ *rste = __pa(table) | _REGION2_ENTRY;
}
- table = *rste & _REGION_ENTRY_ORIGIN;
+ table = __va(*rste & _REGION_ENTRY_ORIGIN);
rc = base_region3_walk(table, addr, next, alloc);
if (rc)
return rc;
@@ -478,13 +586,13 @@ static int base_region2_walk(unsigned long origin, unsigned long addr,
return 0;
}
-static int base_region1_walk(unsigned long origin, unsigned long addr,
+static int base_region1_walk(unsigned long *origin, unsigned long addr,
unsigned long end, int alloc)
{
- unsigned long *rfte, next, table;
+ unsigned long *rfte, next, *table;
int rc;
- rfte = (unsigned long *) origin;
+ rfte = origin;
rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
do {
next = base_region1_addr_end(addr, end);
@@ -494,9 +602,9 @@ static int base_region1_walk(unsigned long origin, unsigned long addr,
table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
if (!table)
return -ENOMEM;
- *rfte = table | _REGION1_ENTRY;
+ *rfte = __pa(table) | _REGION1_ENTRY;
}
- table = *rfte & _REGION_ENTRY_ORIGIN;
+ table = __va(*rfte & _REGION_ENTRY_ORIGIN);
rc = base_region2_walk(table, addr, next, alloc);
if (rc)
return rc;
@@ -515,7 +623,7 @@ static int base_region1_walk(unsigned long origin, unsigned long addr,
*/
void base_asce_free(unsigned long asce)
{
- unsigned long table = asce & _ASCE_ORIGIN;
+ unsigned long *table = __va(asce & _ASCE_ORIGIN);
if (!asce)
return;
@@ -567,7 +675,7 @@ static int base_pgt_cache_init(void)
*/
unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
{
- unsigned long asce, table, end;
+ unsigned long asce, *table, end;
int rc;
if (base_pgt_cache_init())
@@ -578,25 +686,25 @@ unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
if (!table)
return 0;
rc = base_segment_walk(table, addr, end, 1);
- asce = table | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
+ asce = __pa(table) | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
} else if (end <= _REGION2_SIZE) {
table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
if (!table)
return 0;
rc = base_region3_walk(table, addr, end, 1);
- asce = table | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
+ asce = __pa(table) | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
} else if (end <= _REGION1_SIZE) {
table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
if (!table)
return 0;
rc = base_region2_walk(table, addr, end, 1);
- asce = table | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
+ asce = __pa(table) | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
} else {
table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
if (!table)
return 0;
rc = base_region1_walk(table, addr, end, 1);
- asce = table | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
+ asce = __pa(table) | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
}
if (rc) {
base_asce_free(asce);
generated by cgit v1.2.3 (git 2.39.0) at 2024-11-07 22:23:09 +0300