[PATCH v2 3/8] x86/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

David Hildenbrand
2022-03-29T16:47:00Z

Let's use bit 3 to remember PG_anon_exclusive in swap ptes.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/x86/include/asm/pgtable.h | 16 ++++++++++++++++
arch/x86/include/asm/pgtable_64.h | 4 +++-
arch/x86/include/asm/pgtable_types.h | 5 +++++
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 62ab07e24aef..e42e668153e9 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1292,6 +1292,22 @@ static inline void update_mmu_cache_pud(struct vm_area_struct *vma,
{
}

+#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+ return pte_set_flags(pte, _PAGE_SWP_EXCLUSIVE);
+}
+
+static inline int pte_swp_exclusive(pte_t pte)
+{
+ return pte_flags(pte) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ return pte_clear_flags(pte, _PAGE_SWP_EXCLUSIVE);
+}
+
#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
{
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index 56d0399a0cd1..e479491da8d5 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -186,7 +186,7 @@ static inline void native_pgd_clear(pgd_t *pgd)
*
* | ... | 11| 10| 9|8|7|6|5| 4| 3|2| 1|0| <- bit number
* | ... |SW3|SW2|SW1|G|L|D|A|CD|WT|U| W|P| <- bit names
- * | TYPE (59-63) | ~OFFSET (9-58) |0|0|X|X| X| X|F|SD|0| <- swp entry
+ * | TYPE (59-63) | ~OFFSET (9-58) |0|0|X|X| X| E|F|SD|0| <- swp entry
*
* G (8) is aliased and used as a PROT_NONE indicator for
* !present ptes. We need to start storing swap entries above
@@ -203,6 +203,8 @@ static inline void native_pgd_clear(pgd_t *pgd)
* F (2) in swp entry is used to record when a pagetable is
* writeprotected by userfaultfd WP support.
*
+ * E (3) in swp entry is used to rememeber PG_anon_exclusive.
+ *
* Bit 7 in swp entry should be 0 because pmd_present checks not only P,
* but also L and G.
*
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 40497a9020c6..54a8f370046d 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -83,6 +83,11 @@
#define _PAGE_SOFT_DIRTY (_AT(pteval_t, 0))
#endif

+/*
+ * We borrow bit 3 to remember PG_anon_exclusive.
+ */
+#define _PAGE_SWP_EXCLUSIVE _PAGE_PWT
+
/*
* Tracking soft dirty bit when a page goes to a swap is tricky.
* We need a bit which can be stored in pte _and_ not conflict
--
2.35.1