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[S390] merge page_test_dirty and page_clear_dirty
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The page_clear_dirty primitive always sets the default storage key
which resets the access control bits and the fetch protection bit.
That will surprise a KVM guest that sets non-zero access control
bits or the fetch protection bit. Merge page_test_dirty and
page_clear_dirty back to a single function and only clear the
dirty bit from the storage key.

In addition move the function page_test_and_clear_dirty and
page_test_and_clear_young to page.h where they belong. This
requires to change the parameter from a struct page * to a page
frame number.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Martin Schwidefsky committed May 23, 2011
1 parent c26001d commit 2d42552
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Showing 5 changed files with 68 additions and 71 deletions.
56 changes: 50 additions & 6 deletions arch/s390/include/asm/page.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -107,8 +107,8 @@ typedef pte_t *pgtable_t;
#define __pgd(x) ((pgd_t) { (x) } )
#define __pgprot(x) ((pgprot_t) { (x) } )

static inline void
page_set_storage_key(unsigned long addr, unsigned int skey, int mapped)
static inline void page_set_storage_key(unsigned long addr,
unsigned char skey, int mapped)
{
if (!mapped)
asm volatile(".insn rrf,0xb22b0000,%0,%1,8,0"
Expand All @@ -117,15 +117,59 @@ page_set_storage_key(unsigned long addr, unsigned int skey, int mapped)
asm volatile("sske %0,%1" : : "d" (skey), "a" (addr));
}

static inline unsigned int
page_get_storage_key(unsigned long addr)
static inline unsigned char page_get_storage_key(unsigned long addr)
{
unsigned int skey;
unsigned char skey;

asm volatile("iske %0,%1" : "=d" (skey) : "a" (addr), "0" (0));
asm volatile("iske %0,%1" : "=d" (skey) : "a" (addr));
return skey;
}

static inline int page_reset_referenced(unsigned long addr)
{
unsigned int ipm;

asm volatile(
" rrbe 0,%1\n"
" ipm %0\n"
: "=d" (ipm) : "a" (addr) : "cc");
return !!(ipm & 0x20000000);
}

/* Bits int the storage key */
#define _PAGE_CHANGED 0x02 /* HW changed bit */
#define _PAGE_REFERENCED 0x04 /* HW referenced bit */
#define _PAGE_FP_BIT 0x08 /* HW fetch protection bit */
#define _PAGE_ACC_BITS 0xf0 /* HW access control bits */

/*
* Test and clear dirty bit in storage key.
* We can't clear the changed bit atomically. This is a potential
* race against modification of the referenced bit. This function
* should therefore only be called if it is not mapped in any
* address space.
*/
#define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY
static inline int page_test_and_clear_dirty(unsigned long pfn, int mapped)
{
unsigned char skey;

skey = page_get_storage_key(pfn << PAGE_SHIFT);
if (!(skey & _PAGE_CHANGED))
return 0;
page_set_storage_key(pfn << PAGE_SHIFT, skey & ~_PAGE_CHANGED, mapped);
return 1;
}

/*
* Test and clear referenced bit in storage key.
*/
#define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG
static inline int page_test_and_clear_young(unsigned long pfn)
{
return page_reset_referenced(pfn << PAGE_SHIFT);
}

struct page;
void arch_free_page(struct page *page, int order);
void arch_alloc_page(struct page *page, int order);
Expand Down
58 changes: 9 additions & 49 deletions arch/s390/include/asm/pgtable.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -373,10 +373,6 @@ extern unsigned long VMALLOC_START;
#define _ASCE_USER_BITS (_ASCE_SPACE_SWITCH | _ASCE_PRIVATE_SPACE | \
_ASCE_ALT_EVENT)

/* Bits int the storage key */
#define _PAGE_CHANGED 0x02 /* HW changed bit */
#define _PAGE_REFERENCED 0x04 /* HW referenced bit */

/*
* Page protection definitions.
*/
Expand Down Expand Up @@ -555,8 +551,6 @@ static inline void rcp_unlock(pte_t *ptep)
#endif
}

/* forward declaration for SetPageUptodate in page-flags.h*/
static inline void page_clear_dirty(struct page *page, int mapped);
#include <linux/page-flags.h>

static inline void ptep_rcp_copy(pte_t *ptep)
Expand All @@ -566,7 +560,7 @@ static inline void ptep_rcp_copy(pte_t *ptep)
unsigned int skey;
unsigned long *pgste = (unsigned long *) (ptep + PTRS_PER_PTE);

skey = page_get_storage_key(page_to_phys(page));
skey = page_get_storage_key(pte_val(*ptep) >> PAGE_SHIFT);
if (skey & _PAGE_CHANGED) {
set_bit_simple(RCP_GC_BIT, pgste);
set_bit_simple(KVM_UD_BIT, pgste);
Expand Down Expand Up @@ -760,15 +754,17 @@ static inline int kvm_s390_test_and_clear_page_dirty(struct mm_struct *mm,
{
int dirty;
unsigned long *pgste;
unsigned long pfn;
struct page *page;
unsigned int skey;

if (!mm->context.has_pgste)
return -EINVAL;
rcp_lock(ptep);
pgste = (unsigned long *) (ptep + PTRS_PER_PTE);
page = virt_to_page(pte_val(*ptep));
skey = page_get_storage_key(page_to_phys(page));
pfn = pte_val(*ptep) >> PAGE_SHIFT;
page = pfn_to_page(pfn);
skey = page_get_storage_key(pfn);
if (skey & _PAGE_CHANGED) {
set_bit_simple(RCP_GC_BIT, pgste);
set_bit_simple(KVM_UD_BIT, pgste);
Expand All @@ -779,7 +775,7 @@ static inline int kvm_s390_test_and_clear_page_dirty(struct mm_struct *mm,
}
dirty = test_and_clear_bit_simple(KVM_UD_BIT, pgste);
if (skey & _PAGE_CHANGED)
page_clear_dirty(page, 1);
page_set_storage_key(pfn, skey & ~_PAGE_CHANGED, 1);
rcp_unlock(ptep);
return dirty;
}
Expand All @@ -790,16 +786,16 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep)
{
#ifdef CONFIG_PGSTE
unsigned long physpage;
unsigned long pfn;
int young;
unsigned long *pgste;

if (!vma->vm_mm->context.has_pgste)
return 0;
physpage = pte_val(*ptep) & PAGE_MASK;
pfn = pte_val(*ptep) >> PAGE_SHIFT;
pgste = (unsigned long *) (ptep + PTRS_PER_PTE);

young = ((page_get_storage_key(physpage) & _PAGE_REFERENCED) != 0);
young = ((page_get_storage_key(pfn) & _PAGE_REFERENCED) != 0);
rcp_lock(ptep);
if (young)
set_bit_simple(RCP_GR_BIT, pgste);
Expand Down Expand Up @@ -936,42 +932,6 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
__changed; \
})

/*
* Test and clear dirty bit in storage key.
* We can't clear the changed bit atomically. This is a potential
* race against modification of the referenced bit. This function
* should therefore only be called if it is not mapped in any
* address space.
*/
#define __HAVE_ARCH_PAGE_TEST_DIRTY
static inline int page_test_dirty(struct page *page)
{
return (page_get_storage_key(page_to_phys(page)) & _PAGE_CHANGED) != 0;
}

#define __HAVE_ARCH_PAGE_CLEAR_DIRTY
static inline void page_clear_dirty(struct page *page, int mapped)
{
page_set_storage_key(page_to_phys(page), PAGE_DEFAULT_KEY, mapped);
}

/*
* Test and clear referenced bit in storage key.
*/
#define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG
static inline int page_test_and_clear_young(struct page *page)
{
unsigned long physpage = page_to_phys(page);
int ccode;

asm volatile(
" rrbe 0,%1\n"
" ipm %0\n"
" srl %0,28\n"
: "=d" (ccode) : "a" (physpage) : "cc" );
return ccode & 2;
}

/*
* Conversion functions: convert a page and protection to a page entry,
* and a page entry and page directory to the page they refer to.
Expand Down
12 changes: 4 additions & 8 deletions include/asm-generic/pgtable.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -184,22 +184,18 @@ static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif

#ifndef __HAVE_ARCH_PAGE_TEST_DIRTY
#define page_test_dirty(page) (0)
#ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY
#define page_test_and_clear_dirty(pfn, mapped) (0)
#endif

#ifndef __HAVE_ARCH_PAGE_CLEAR_DIRTY
#define page_clear_dirty(page, mapped) do { } while (0)
#endif

#ifndef __HAVE_ARCH_PAGE_TEST_DIRTY
#ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY
#define pte_maybe_dirty(pte) pte_dirty(pte)
#else
#define pte_maybe_dirty(pte) (1)
#endif

#ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG
#define page_test_and_clear_young(page) (0)
#define page_test_and_clear_young(pfn) (0)
#endif

#ifndef __HAVE_ARCH_PGD_OFFSET_GATE
Expand Down
2 changes: 1 addition & 1 deletion include/linux/page-flags.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -308,7 +308,7 @@ static inline void SetPageUptodate(struct page *page)
{
#ifdef CONFIG_S390
if (!test_and_set_bit(PG_uptodate, &page->flags))
page_clear_dirty(page, 0);
page_set_storage_key(page_to_pfn(page), PAGE_DEFAULT_KEY, 0);
#else
/*
* Memory barrier must be issued before setting the PG_uptodate bit,
Expand Down
11 changes: 4 additions & 7 deletions mm/rmap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -719,7 +719,7 @@ int page_referenced(struct page *page,
unlock_page(page);
}
out:
if (page_test_and_clear_young(page))
if (page_test_and_clear_young(page_to_pfn(page)))
referenced++;

return referenced;
Expand Down Expand Up @@ -785,10 +785,8 @@ int page_mkclean(struct page *page)
struct address_space *mapping = page_mapping(page);
if (mapping) {
ret = page_mkclean_file(mapping, page);
if (page_test_dirty(page)) {
page_clear_dirty(page, 1);
if (page_test_and_clear_dirty(page_to_pfn(page), 1))
ret = 1;
}
}
}

Expand Down Expand Up @@ -981,10 +979,9 @@ void page_remove_rmap(struct page *page)
* not if it's in swapcache - there might be another pte slot
* containing the swap entry, but page not yet written to swap.
*/
if ((!PageAnon(page) || PageSwapCache(page)) && page_test_dirty(page)) {
page_clear_dirty(page, 1);
if ((!PageAnon(page) || PageSwapCache(page)) &&
page_test_and_clear_dirty(page_to_pfn(page), 1))
set_page_dirty(page);
}
/*
* Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
* and not charged by memcg for now.
Expand Down

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