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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2013-07-24 00:11:42 +0400
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2013-08-29 15:20:11 +0400
commit0944fe3f4a323f436180d39402cae7f9c46ead17 (patch)
tree7b2ada69ff7e3c1fae20ec0b1dffe5e0d0ec2cc6 /arch/s390/mm/hugetlbpage.c
parentfbd70035fb2b03deb346052084794bc1d0e25aa2 (diff)
downloadlinux-0944fe3f4a323f436180d39402cae7f9c46ead17.tar.xz
s390/mm: implement software referenced bits
The last remaining use for the storage key of the s390 architecture is reference counting. The alternative is to make page table entries invalid while they are old. On access the fault handler marks the pte/pmd as young which makes the pte/pmd valid if the access rights allow read access. The pte/pmd invalidations required for software managed reference bits cost a bit of performance, on the other hand the RRBE/RRBM instructions to read and reset the referenced bits are quite expensive as well. Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/mm/hugetlbpage.c')
-rw-r--r--arch/s390/mm/hugetlbpage.c58
1 files changed, 39 insertions, 19 deletions
diff --git a/arch/s390/mm/hugetlbpage.c b/arch/s390/mm/hugetlbpage.c
index b0bd0ae17796..248445f92604 100644
--- a/arch/s390/mm/hugetlbpage.c
+++ b/arch/s390/mm/hugetlbpage.c
@@ -10,19 +10,25 @@
static inline pmd_t __pte_to_pmd(pte_t pte)
{
- int none, prot;
+ int none, young, prot;
pmd_t pmd;
/*
- * Convert encoding pte bits pmd bits
- * .IR.....wdtp ..R...I.....
- * empty .10.....0000 -> ..0...1.....
- * prot-none, clean .11.....0001 -> ..1...1.....
- * prot-none, dirty .10.....0101 -> ..1...1.....
- * read-only, clean .01.....0001 -> ..1...0.....
- * read-only, dirty .01.....0101 -> ..1...0.....
- * read-write, clean .01.....1001 -> ..0...0.....
- * read-write, dirty .00.....1101 -> ..0...0.....
+ * Convert encoding pte bits pmd bits
+ * .IR...wrdytp ..R...I...y.
+ * empty .10...000000 -> ..0...1...0.
+ * prot-none, clean, old .11...000001 -> ..0...1...1.
+ * prot-none, clean, young .11...000101 -> ..1...1...1.
+ * prot-none, dirty, old .10...001001 -> ..0...1...1.
+ * prot-none, dirty, young .10...001101 -> ..1...1...1.
+ * read-only, clean, old .11...010001 -> ..1...1...0.
+ * read-only, clean, young .01...010101 -> ..1...0...1.
+ * read-only, dirty, old .11...011001 -> ..1...1...0.
+ * read-only, dirty, young .01...011101 -> ..1...0...1.
+ * read-write, clean, old .11...110001 -> ..0...1...0.
+ * read-write, clean, young .01...110101 -> ..0...0...1.
+ * read-write, dirty, old .10...111001 -> ..0...1...0.
+ * read-write, dirty, young .00...111101 -> ..0...0...1.
* Huge ptes are dirty by definition, a clean pte is made dirty
* by the conversion.
*/
@@ -31,9 +37,14 @@ static inline pmd_t __pte_to_pmd(pte_t pte)
if (pte_val(pte) & _PAGE_INVALID)
pmd_val(pmd) |= _SEGMENT_ENTRY_INVALID;
none = (pte_val(pte) & _PAGE_PRESENT) &&
- (pte_val(pte) & _PAGE_INVALID);
- prot = (pte_val(pte) & _PAGE_PROTECT);
- if (prot || none)
+ !(pte_val(pte) & _PAGE_READ) &&
+ !(pte_val(pte) & _PAGE_WRITE);
+ prot = (pte_val(pte) & _PAGE_PROTECT) &&
+ !(pte_val(pte) & _PAGE_WRITE);
+ young = pte_val(pte) & _PAGE_YOUNG;
+ if (none || young)
+ pmd_val(pmd) |= _SEGMENT_ENTRY_YOUNG;
+ if (prot || (none && young))
pmd_val(pmd) |= _SEGMENT_ENTRY_PROTECT;
} else
pmd_val(pmd) = _SEGMENT_ENTRY_INVALID;
@@ -46,11 +57,14 @@ static inline pte_t __pmd_to_pte(pmd_t pmd)
/*
* Convert encoding pmd bits pte bits
- * ..R...I..... .IR.....wdtp
- * empty ..0...1..... -> .10.....0000
- * prot-none, young ..1...1..... -> .10.....0101
- * read-only, young ..1...0..... -> .01.....0101
- * read-write, young ..0...0..... -> .00.....1101
+ * ..R...I...y. .IR...wrdytp
+ * empty ..0...1...0. -> .10...000000
+ * prot-none, old ..0...1...1. -> .10...001001
+ * prot-none, young ..1...1...1. -> .10...001101
+ * read-only, old ..1...1...0. -> .11...011001
+ * read-only, young ..1...0...1. -> .01...011101
+ * read-write, old ..0...1...0. -> .10...111001
+ * read-write, young ..0...0...1. -> .00...111101
* Huge ptes are dirty by definition
*/
if (pmd_present(pmd)) {
@@ -58,11 +72,17 @@ static inline pte_t __pmd_to_pte(pmd_t pmd)
(pmd_val(pmd) & PAGE_MASK);
if (pmd_val(pmd) & _SEGMENT_ENTRY_INVALID)
pte_val(pte) |= _PAGE_INVALID;
- else {
+ if (pmd_prot_none(pmd)) {
+ if (pmd_val(pmd) & _SEGMENT_ENTRY_PROTECT)
+ pte_val(pte) |= _PAGE_YOUNG;
+ } else {
+ pte_val(pte) |= _PAGE_READ;
if (pmd_val(pmd) & _SEGMENT_ENTRY_PROTECT)
pte_val(pte) |= _PAGE_PROTECT;
else
pte_val(pte) |= _PAGE_WRITE;
+ if (pmd_val(pmd) & _SEGMENT_ENTRY_YOUNG)
+ pte_val(pte) |= _PAGE_YOUNG;
}
} else
pte_val(pte) = _PAGE_INVALID;