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[S390] introduce dirty bit for kvm live migration

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This patch defines a dirty bit in the PGSTE that can be used to implement
dirty pages logging for KVM's live migration. The bit is set in the
ptep_rcp_copy function, which is called to save dirty and referenced information
from the storage key in the PGSTE. The bit can be tested and reset by KVM using
the kvm_s390_test_and_clear_page_dirty function that is introduced by this patch.

Acked-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Florian Funke <ffunke@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Florian Funke 2008-10-10 21:33:26 +02:00 committed by Martin Schwidefsky
parent ab1d848fd6
commit 15e86b0c75
1 changed files with 43 additions and 2 deletions
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45
arch/s390/include/asm/pgtable.h
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@ -281,6 +281,9 @@ extern char empty_zero_page[PAGE_SIZE];
#define RCP_GR_BIT 50
#define RCP_GC_BIT 49
/* User dirty bit for KVM's migration feature */
#define KVM_UD_BIT 47
#ifndef __s390x__
/* Bits in the segment table address-space-control-element */
@ -575,12 +578,16 @@ static inline void ptep_rcp_copy(pte_t *ptep)
unsigned long *pgste = (unsigned long *) (ptep + PTRS_PER_PTE);
skey = page_get_storage_key(page_to_phys(page));
if (skey & _PAGE_CHANGED)
if (skey & _PAGE_CHANGED) {
set_bit_simple(RCP_GC_BIT, pgste);
set_bit_simple(KVM_UD_BIT, pgste);
}
if (skey & _PAGE_REFERENCED)
set_bit_simple(RCP_GR_BIT, pgste);
if (test_and_clear_bit_simple(RCP_HC_BIT, pgste))
if (test_and_clear_bit_simple(RCP_HC_BIT, pgste)) {
SetPageDirty(page);
set_bit_simple(KVM_UD_BIT, pgste);
}
if (test_and_clear_bit_simple(RCP_HR_BIT, pgste))
SetPageReferenced(page);
#endif
@ -744,6 +751,40 @@ static inline pte_t pte_mkspecial(pte_t pte)
return pte;
}
#ifdef CONFIG_PGSTE
/*
* Get (and clear) the user dirty bit for a PTE.
*/
static inline int kvm_s390_test_and_clear_page_dirty(struct mm_struct *mm,
pte_t *ptep)
{
int dirty;
unsigned long *pgste;
struct page *page;
unsigned int skey;
if (!mm->context.pgstes)
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));
if (skey & _PAGE_CHANGED) {
set_bit_simple(RCP_GC_BIT, pgste);
set_bit_simple(KVM_UD_BIT, pgste);
}
if (test_and_clear_bit_simple(RCP_HC_BIT, pgste)) {
SetPageDirty(page);
set_bit_simple(KVM_UD_BIT, pgste);
}
dirty = test_and_clear_bit_simple(KVM_UD_BIT, pgste);
if (skey & _PAGE_CHANGED)
page_clear_dirty(page);
rcp_unlock(ptep);
return dirty;
}
#endif
#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep)