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Commit 15e86b0c authored by Florian Funke's avatar Florian Funke Committed by Martin Schwidefsky
Browse files

[S390] introduce dirty bit for kvm live migration 



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: default avatarCarsten Otte <cotte@de.ibm.com>
Signed-off-by: default avatarFlorian Funke <ffunke@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent ab1d848f

arch/s390/include/asm/pgtable.h

+43 −2
Original line number Diff line number Diff line
@@ -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)