[RFC v2 09/43] PKRAM: track preserved pages in a physical mapping pagetable
Anthony Yznaga
anthony.yznaga at oracle.com
Tue Mar 30 22:35:44 BST 2021
Later patches in this series will need a way to efficiently identify
physically contiguous ranges of preserved pages independent of their
virtual addresses. To facilitate this all pages to be preserved across
kexec are added to a pseudo identity mapping pagetable.
The pagetable makes use of the existing architecture definitions for
building a memory mapping pagetable except that a bitmap is used to
represent the presence or absence of preserved pages at the PTE level.
Signed-off-by: Anthony Yznaga <anthony.yznaga at oracle.com>
---
mm/Makefile | 2 +-
mm/pkram.c | 30 +++-
mm/pkram_pagetable.c | 376 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 404 insertions(+), 4 deletions(-)
create mode 100644 mm/pkram_pagetable.c
diff --git a/mm/Makefile b/mm/Makefile
index ab3a724769b5..f5c0dd0a3707 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -120,4 +120,4 @@ obj-$(CONFIG_MEMFD_CREATE) += memfd.o
obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o
obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
-obj-$(CONFIG_PKRAM) += pkram.o
+obj-$(CONFIG_PKRAM) += pkram.o pkram_pagetable.o
diff --git a/mm/pkram.c b/mm/pkram.c
index 2809371a9aec..a9e6cd8ca084 100644
--- a/mm/pkram.c
+++ b/mm/pkram.c
@@ -103,6 +103,9 @@ struct pkram_super_block {
static unsigned long pkram_sb_pfn __initdata;
static struct pkram_super_block *pkram_sb;
+extern int pkram_add_identity_map(struct page *page);
+extern void pkram_remove_identity_map(struct page *page);
+
/*
* For convenience sake PKRAM nodes are kept in an auxiliary doubly-linked list
* connected through the lru field of the page struct.
@@ -121,11 +124,24 @@ static int __init parse_pkram_sb_pfn(char *arg)
static inline struct page *pkram_alloc_page(gfp_t gfp_mask)
{
- return alloc_page(gfp_mask);
+ struct page *page;
+ int err;
+
+ page = alloc_page(gfp_mask);
+ if (page) {
+ err = pkram_add_identity_map(page);
+ if (err) {
+ __free_page(page);
+ page = NULL;
+ }
+ }
+
+ return page;
}
static inline void pkram_free_page(void *addr)
{
+ pkram_remove_identity_map(virt_to_page(addr));
free_page((unsigned long)addr);
}
@@ -163,6 +179,7 @@ static void pkram_truncate_link(struct pkram_link *link)
if (!p)
continue;
page = pfn_to_page(PHYS_PFN(p));
+ pkram_remove_identity_map(page);
put_page(page);
}
}
@@ -615,10 +632,15 @@ static int __pkram_save_page(struct pkram_access *pa, struct page *page,
int pkram_save_file_page(struct pkram_access *pa, struct page *page)
{
struct pkram_node *node = pa->ps->node;
+ int err;
BUG_ON((node->flags & PKRAM_ACCMODE_MASK) != PKRAM_SAVE);
- return __pkram_save_page(pa, page, page->index);
+ err = __pkram_save_page(pa, page, page->index);
+ if (!err)
+ err = pkram_add_identity_map(page);
+
+ return err;
}
static int __pkram_bytes_save_page(struct pkram_access *pa, struct page *page)
@@ -652,6 +674,8 @@ static struct page *__pkram_prep_load_page(pkram_entry_t p)
prep_transhuge_page(page);
}
+ pkram_remove_identity_map(page);
+
return page;
}
@@ -898,7 +922,7 @@ static int __init pkram_init_sb(void)
if (!pkram_sb) {
struct page *page;
- page = pkram_alloc_page(GFP_KERNEL | __GFP_ZERO);
+ page = alloc_page(GFP_KERNEL | __GFP_ZERO);
if (!page) {
pr_err("PKRAM: Failed to allocate super block\n");
return 0;
diff --git a/mm/pkram_pagetable.c b/mm/pkram_pagetable.c
new file mode 100644
index 000000000000..9c5443bd7686
--- /dev/null
+++ b/mm/pkram_pagetable.c
@@ -0,0 +1,376 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bitops.h>
+//#include <asm/pgtable.h>
+#include <linux/mm.h>
+
+static pgd_t *pkram_pgd;
+static DEFINE_SPINLOCK(pkram_pgd_lock);
+
+#define set_p4d(p4dp, p4d) WRITE_ONCE(*(p4dp), (p4d))
+
+#define PKRAM_PTE_BM_BYTES (PTRS_PER_PTE / BITS_PER_BYTE)
+#define PKRAM_PTE_BM_MASK (PAGE_SIZE / PKRAM_PTE_BM_BYTES - 1)
+
+static pmd_t make_bitmap_pmd(unsigned long *bitmap)
+{
+ unsigned long val;
+
+ val = __pa(ALIGN_DOWN((unsigned long)bitmap, PAGE_SIZE));
+ val |= (((unsigned long)bitmap & ~PAGE_MASK) / PKRAM_PTE_BM_BYTES);
+
+ return __pmd(val);
+}
+
+static unsigned long *get_bitmap_addr(pmd_t pmd)
+{
+ unsigned long val, off;
+
+ val = pmd_val(pmd);
+ off = (val & PKRAM_PTE_BM_MASK) * PKRAM_PTE_BM_BYTES;
+
+ val = (val & PAGE_MASK) + off;
+
+ return __va(val);
+}
+
+int pkram_add_identity_map(struct page *page)
+{
+ unsigned long paddr;
+ unsigned long *bitmap;
+ unsigned int index;
+ struct page *pg;
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+
+ if (!pkram_pgd) {
+ spin_lock(&pkram_pgd_lock);
+ if (!pkram_pgd) {
+ pg = alloc_page(GFP_ATOMIC|__GFP_ZERO);
+ if (!pg)
+ goto nomem;
+ pkram_pgd = page_address(pg);
+ }
+ spin_unlock(&pkram_pgd_lock);
+ }
+
+ paddr = __pa(page_address(page));
+ pgd = pkram_pgd;
+ pgd += pgd_index(paddr);
+ if (pgd_none(*pgd)) {
+ spin_lock(&pkram_pgd_lock);
+ if (pgd_none(*pgd)) {
+ pg = alloc_page(GFP_ATOMIC|__GFP_ZERO);
+ if (!pg)
+ goto nomem;
+ p4d = page_address(pg);
+ set_pgd(pgd, __pgd(__pa(p4d)));
+ }
+ spin_unlock(&pkram_pgd_lock);
+ }
+ p4d = p4d_offset(pgd, paddr);
+ if (p4d_none(*p4d)) {
+ spin_lock(&pkram_pgd_lock);
+ if (p4d_none(*p4d)) {
+ pg = alloc_page(GFP_ATOMIC|__GFP_ZERO);
+ if (!pg)
+ goto nomem;
+ pud = page_address(pg);
+ set_p4d(p4d, __p4d(__pa(pud)));
+ }
+ spin_unlock(&pkram_pgd_lock);
+ }
+ pud = pud_offset(p4d, paddr);
+ if (pud_none(*pud)) {
+ spin_lock(&pkram_pgd_lock);
+ if (pud_none(*pud)) {
+ pg = alloc_page(GFP_ATOMIC|__GFP_ZERO);
+ if (!pg)
+ goto nomem;
+ pmd = page_address(pg);
+ set_pud(pud, __pud(__pa(pmd)));
+ }
+ spin_unlock(&pkram_pgd_lock);
+ }
+ pmd = pmd_offset(pud, paddr);
+ if (pmd_none(*pmd)) {
+ spin_lock(&pkram_pgd_lock);
+ if (pmd_none(*pmd)) {
+ if (PageTransHuge(page)) {
+ set_pmd(pmd, pmd_mkhuge(*pmd));
+ spin_unlock(&pkram_pgd_lock);
+ goto done;
+ }
+ bitmap = bitmap_zalloc(PTRS_PER_PTE, GFP_ATOMIC);
+ if (!bitmap)
+ goto nomem;
+ set_pmd(pmd, make_bitmap_pmd(bitmap));
+ } else {
+ BUG_ON(pmd_large(*pmd));
+ bitmap = get_bitmap_addr(*pmd);
+ }
+ spin_unlock(&pkram_pgd_lock);
+ } else {
+ BUG_ON(pmd_large(*pmd));
+ bitmap = get_bitmap_addr(*pmd);
+ }
+
+ index = pte_index(paddr);
+ BUG_ON(test_bit(index, bitmap));
+ set_bit(index, bitmap);
+ smp_mb__after_atomic();
+ if (bitmap_full(bitmap, PTRS_PER_PTE))
+ set_pmd(pmd, pmd_mkhuge(*pmd));
+done:
+ return 0;
+nomem:
+ return -ENOMEM;
+}
+
+void pkram_remove_identity_map(struct page *page)
+{
+ unsigned long *bitmap;
+ unsigned long paddr;
+ unsigned int index;
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+
+ /*
+ * pkram_pgd will be null when freeing metadata pages after a reboot
+ */
+ if (!pkram_pgd)
+ return;
+
+ paddr = __pa(page_address(page));
+ pgd = pkram_pgd;
+ pgd += pgd_index(paddr);
+ if (pgd_none(*pgd)) {
+ WARN_ONCE(1, "PKRAM: %s: no pgd for 0x%lx\n", __func__, paddr);
+ return;
+ }
+ p4d = p4d_offset(pgd, paddr);
+ if (p4d_none(*p4d)) {
+ WARN_ONCE(1, "PKRAM: %s: no p4d for 0x%lx\n", __func__, paddr);
+ return;
+ }
+ pud = pud_offset(p4d, paddr);
+ if (pud_none(*pud)) {
+ WARN_ONCE(1, "PKRAM: %s: no pud for 0x%lx\n", __func__, paddr);
+ return;
+ }
+ pmd = pmd_offset(pud, paddr);
+ if (pmd_none(*pmd)) {
+ WARN_ONCE(1, "PKRAM: %s: no pmd for 0x%lx\n", __func__, paddr);
+ return;
+ }
+ if (PageTransHuge(page)) {
+ BUG_ON(!pmd_large(*pmd));
+ pmd_clear(pmd);
+ return;
+ }
+
+ if (pmd_large(*pmd)) {
+ spin_lock(&pkram_pgd_lock);
+ if (pmd_large(*pmd))
+ set_pmd(pmd, __pmd(pte_val(pte_clrhuge(*(pte_t *)pmd))));
+ spin_unlock(&pkram_pgd_lock);
+ }
+
+ bitmap = get_bitmap_addr(*pmd);
+ index = pte_index(paddr);
+ clear_bit(index, bitmap);
+ smp_mb__after_atomic();
+
+ spin_lock(&pkram_pgd_lock);
+ if (!pmd_none(*pmd) && bitmap_empty(bitmap, PTRS_PER_PTE)) {
+ pmd_clear(pmd);
+ spin_unlock(&pkram_pgd_lock);
+ bitmap_free(bitmap);
+ } else {
+ spin_unlock(&pkram_pgd_lock);
+ }
+}
+
+struct pkram_pg_state {
+ int (*range_cb)(unsigned long base, unsigned long size, void *private);
+ unsigned long start_addr;
+ unsigned long curr_addr;
+ unsigned long min_addr;
+ unsigned long max_addr;
+ void *private;
+ bool tracking;
+};
+
+#define pgd_none(a) (pgtable_l5_enabled() ? pgd_none(a) : p4d_none(__p4d(pgd_val(a))))
+
+static int note_page(struct pkram_pg_state *st, unsigned long addr, bool present)
+{
+ if (!st->tracking && present) {
+ if (addr >= st->max_addr)
+ return 1;
+ /*
+ * addr can be < min_addr if the page straddles the
+ * boundary
+ */
+ st->start_addr = max(addr, st->min_addr);
+ st->tracking = true;
+ } else if (st->tracking) {
+ unsigned long base, size;
+ int ret;
+
+ /* Continue tracking if upper bound has not been reached */
+ if (present && addr < st->max_addr)
+ return 0;
+
+ addr = min(addr, st->max_addr);
+
+ base = st->start_addr;
+ size = addr - st->start_addr;
+ st->tracking = false;
+
+ ret = st->range_cb(base, size, st->private);
+
+ if (addr == st->max_addr)
+ return 1;
+ else
+ return ret;
+ }
+
+ return 0;
+}
+
+static int walk_pte_level(struct pkram_pg_state *st, pmd_t addr, unsigned long P)
+{
+ unsigned long *bitmap;
+ int present;
+ int i, ret;
+
+ bitmap = get_bitmap_addr(addr);
+ for (i = 0; i < PTRS_PER_PTE; i++) {
+ unsigned long curr_addr = P + i * PAGE_SIZE;
+
+ if (curr_addr < st->min_addr)
+ continue;
+ present = test_bit(i, bitmap);
+ ret = note_page(st, curr_addr, present);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+static int walk_pmd_level(struct pkram_pg_state *st, pud_t addr, unsigned long P)
+{
+ pmd_t *start;
+ int i, ret;
+
+ start = (pmd_t *)pud_page_vaddr(addr);
+ for (i = 0; i < PTRS_PER_PMD; i++, start++) {
+ unsigned long curr_addr = P + i * PMD_SIZE;
+
+ if (curr_addr + PMD_SIZE <= st->min_addr)
+ continue;
+ if (!pmd_none(*start)) {
+ if (pmd_large(*start))
+ ret = note_page(st, curr_addr, true);
+ else
+ ret = walk_pte_level(st, *start, curr_addr);
+ } else
+ ret = note_page(st, curr_addr, false);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+static int walk_pud_level(struct pkram_pg_state *st, p4d_t addr, unsigned long P)
+{
+ pud_t *start;
+ int i, ret;
+
+ start = (pud_t *)p4d_page_vaddr(addr);
+ for (i = 0; i < PTRS_PER_PUD; i++, start++) {
+ unsigned long curr_addr = P + i * PUD_SIZE;
+
+ if (curr_addr + PUD_SIZE <= st->min_addr)
+ continue;
+ if (!pud_none(*start)) {
+ if (pud_large(*start))
+ ret = note_page(st, curr_addr, true);
+ else
+ ret = walk_pmd_level(st, *start, curr_addr);
+ } else
+ ret = note_page(st, curr_addr, false);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+static int walk_p4d_level(struct pkram_pg_state *st, pgd_t addr, unsigned long P)
+{
+ p4d_t *start;
+ int i, ret;
+
+ if (PTRS_PER_P4D == 1)
+ return walk_pud_level(st, __p4d(pgd_val(addr)), P);
+
+ start = (p4d_t *)pgd_page_vaddr(addr);
+ for (i = 0; i < PTRS_PER_P4D; i++, start++) {
+ unsigned long curr_addr = P + i * P4D_SIZE;
+
+ if (curr_addr + P4D_SIZE <= st->min_addr)
+ continue;
+ if (!p4d_none(*start)) {
+ if (p4d_large(*start))
+ ret = note_page(st, curr_addr, true);
+ else
+ ret = walk_pud_level(st, *start, curr_addr);
+ } else
+ ret = note_page(st, curr_addr, false);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+void pkram_walk_pgt(struct pkram_pg_state *st, pgd_t *pgd)
+{
+ pgd_t *start = pgd;
+ int i, ret = 0;
+
+ for (i = 0; i < PTRS_PER_PGD; i++, start++) {
+ unsigned long curr_addr = i * PGDIR_SIZE;
+
+ if (curr_addr + PGDIR_SIZE <= st->min_addr)
+ continue;
+ if (!pgd_none(*start))
+ ret = walk_p4d_level(st, *start, curr_addr);
+ else
+ ret = note_page(st, curr_addr, false);
+ if (ret)
+ break;
+ }
+}
+
+void pkram_find_preserved(unsigned long start, unsigned long end, void *private, int (*callback)(unsigned long base, unsigned long size, void *private))
+{
+ struct pkram_pg_state st = {
+ .range_cb = callback,
+ .min_addr = start,
+ .max_addr = end,
+ .private = private,
+ };
+
+ if (!pkram_pgd)
+ return;
+
+ pkram_walk_pgt(&st, pkram_pgd);
+}
--
1.8.3.1
More information about the kexec
mailing list