With this patch we use 0x8000000000000000UL (_PAGE_PRESENT) to indicate a valid
pgd/pud/pmd entry. We also switch the p**_present() to look at this bit.
With pmd_present, we have a special case. We need to make sure we consider a
pmd marked invalid during THP split as present. Right now we clear the
_PAGE_PRESENT bit during a pmdp_invalidate. Inorder to consider this special
case we add a new pte bit _PAGE_INVALID (mapped to _RPAGE_SW0). This bit is
only used with _PAGE_PRESENT cleared. Hence we are not really losing a pte bit
for this special case. pmd_present is also updated to look at _PAGE_INVALID.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
arch/powerpc/include/asm/book3s/64/hash.h | 5 +++++
arch/powerpc/include/asm/book3s/64/pgtable.h | 23 +++++++++++++++++---
arch/powerpc/mm/hash_utils_64.c | 6 ++---
arch/powerpc/mm/pgtable-book3s64.c | 2 +-
4 files changed, 29 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 0387b155f13d..a371ac7c3183 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -16,6 +16,11 @@
#include <asm/book3s/64/hash-4k.h>
#endif
+/* Bits to set in a PMD/PUD/PGD entry valid bit*/
+#define HASH_PMD_VAL_BITS (0x8000000000000000UL)
+#define HASH_PUD_VAL_BITS (0x8000000000000000UL)
+#define HASH_PGD_VAL_BITS (0x8000000000000000UL)
+
/*
* Size of EA range mapped by our pagetables.
*/
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 676118743a06..fce9ce8781a0 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -44,6 +44,15 @@
#define _PAGE_PTE 0x4000000000000000UL /* distinguishes PTEs from pointers */
#define _PAGE_PRESENT 0x8000000000000000UL /* pte contains a translation */
+/*
+ * We need to mark a pmd pte invalid while splitting. We can do that by clearing the
+ * _PAGE_PRESENT bit. But then that will be taken as a swap pte. Inorder to differentiate
+ * between two use a SW field when invalidating. We don't add a special bit to indicate
+ * swap pte because that is also used for migration ptes, and we do back and forth between
+ * a valid pte entry and migration ptes. So any information in the software bits will be
+ * lost if we overload those bits.
+ */
+#define _PAGE_INVALID _RPAGE_SW0
/*
* Top and bottom bits of RPN which can be used by hash
@@ -859,8 +868,16 @@ static inline int pmd_none(pmd_t pmd)
static inline int pmd_present(pmd_t pmd)
{
+ /*
+ * A pmd is considerent present if _PAGE_PRESENT is set.
+ * We also need to consider the pmd present which is marked
+ * invalid during a split. Hence we look for _PAGE_INVALID
+ * if we find _PAGE_PRESENT cleared.
+ */
+ if (pmd_raw(pmd) & cpu_to_be64(_PAGE_PRESENT | _PAGE_INVALID))
+ return true;
- return !pmd_none(pmd);
+ return false;
}
static inline int pmd_bad(pmd_t pmd)
@@ -887,7 +904,7 @@ static inline int pud_none(pud_t pud)
static inline int pud_present(pud_t pud)
{
- return !pud_none(pud);
+ return (pud_raw(pud) & cpu_to_be64(_PAGE_PRESENT));
}
extern struct page *pud_page(pud_t pud);
@@ -934,7 +951,7 @@ static inline int pgd_none(pgd_t pgd)
static inline int pgd_present(pgd_t pgd)
{
- return !pgd_none(pgd);
+ return (pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT));
}
static inline pte_t pgd_pte(pgd_t pgd)
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 5a72e980e25a..7ce7fa5397d5 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -1002,9 +1002,9 @@ void __init hash__early_init_mmu(void)
* 4k use hugepd format, so for hash set then to
* zero
*/
- __pmd_val_bits = 0;
- __pud_val_bits = 0;
- __pgd_val_bits = 0;
+ __pmd_val_bits = HASH_PMD_VAL_BITS;
+ __pud_val_bits = HASH_PUD_VAL_BITS;
+ __pgd_val_bits = HASH_PGD_VAL_BITS;
__kernel_virt_start = H_KERN_VIRT_START;
__kernel_virt_size = H_KERN_VIRT_SIZE;
diff --git a/arch/powerpc/mm/pgtable-book3s64.c b/arch/powerpc/mm/pgtable-book3s64.c
index 4afbfbb64bfd..24346ab4cd37 100644
--- a/arch/powerpc/mm/pgtable-book3s64.c
+++ b/arch/powerpc/mm/pgtable-book3s64.c
@@ -106,7 +106,7 @@ pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
{
unsigned long old_pmd;
- old_pmd = pmd_hugepage_update(vma->vm_mm, address, pmdp, _PAGE_PRESENT, 0);
+ old_pmd = pmd_hugepage_update(vma->vm_mm, address, pmdp, _PAGE_PRESENT, _PAGE_INVALID);
flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
/*
* This ensures that generic code that rely on IRQ disabling
--
2.17.1
