When splitting a huge pmd pte, we need to mark the pmd entry invalid. We
can do that by clearing _PAGE_PRESENT bit. But then that will be taken as a
swap pte. In order to differentiate between the two use a software pte bit
when invalidating.
For regular pte, due to bd5050e38aec ("powerpc/mm/radix: Change pte relax
sequence to handle nest MMU hang") we need to mark the pte entry invalid when
relaxing access permission. Instead of marking pte_none which can result in
different page table walk routines possibly skipping this pte entry, invalidate
it but still keep it marked present.
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
arch/powerpc/include/asm/book3s/64/pgtable.h | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h
b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 676118743a06..13a688fc8cd0 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -44,6 +44,16 @@
#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. In order
to
+ * differentiate between two use a SW field when invalidating.
+ *
+ * We do that temporary invalidate for regular pte entry in
ptep_set_access_flags
+ *
+ * This is used only when _PAGE_PRESENT is cleared.
+ */
+#define _PAGE_INVALID _RPAGE_SW0
/*
* Top and bottom bits of RPN which can be used by hash
@@ -568,7 +578,13 @@ static inline pte_t pte_clear_savedwrite(pte_t pte)
static inline int pte_present(pte_t pte)
{
- return !!(pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT));
+ /*
+ * A pte is considerent present if _PAGE_PRESENT is set.
+ * We also need to consider the pte present which is marked
+ * invalid during ptep_set_access_flags. Hence we look for _PAGE_INVALID
+ * if we find _PAGE_PRESENT cleared.
+ */
+ return !!(pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_INVALID));
}
#ifdef CONFIG_PPC_MEM_KEYS
--
2.17.1
