KVM: s390/mm: use software dirty bit detection for user dirty tracking
Switch the user dirty bit detection used for migration from the hardware
provided host change-bit in the pgste to a fault based detection method.
This reduced the dependency of the host from the storage key to a point
where it becomes possible to enable the RCP bypass for KVM guests.
The fault based dirty detection will only indicate changes caused
by accesses via the guest address space. The hardware based method
can detect all changes, even those caused by I/O or accesses via the
kernel page table. The KVM/qemu code needs to take this into account.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 02a8607..1ddf975 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -832,6 +832,7 @@
}
spin_unlock(&gmap_notifier_lock);
}
+EXPORT_SYMBOL_GPL(gmap_do_ipte_notify);
static inline int page_table_with_pgste(struct page *page)
{
@@ -864,8 +865,7 @@
atomic_set(&page->_mapcount, 0);
table = (unsigned long *) page_to_phys(page);
clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
- clear_table(table + PTRS_PER_PTE, PGSTE_HR_BIT | PGSTE_HC_BIT,
- PAGE_SIZE/2);
+ clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
return table;
}
@@ -1005,7 +1005,7 @@
/* changing the guest storage key is considered a change of the page */
if ((pgste_val(new) ^ pgste_val(old)) &
(PGSTE_ACC_BITS | PGSTE_FP_BIT | PGSTE_GR_BIT | PGSTE_GC_BIT))
- pgste_val(new) |= PGSTE_HC_BIT;
+ pgste_val(new) |= PGSTE_UC_BIT;
pgste_set_unlock(ptep, new);
pte_unmap_unlock(*ptep, ptl);