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kvm: Persistent per kvmslot dirty bitmap 

When synchronizing dirty bitmap from kernel KVM we do it in a
per-kvmslot fashion and we allocate the userspace bitmap for each of
the ioctl.  This patch instead make the bitmap cache be persistent
then we don't need to g_malloc0() every time.

More importantly, the cached per-kvmslot dirty bitmap will be further
used when we want to add support for the KVM_CLEAR_DIRTY_LOG and this
cached bitmap will be used to guarantee we won't clear any unknown
dirty bits otherwise that can be a severe data loss issue for
migration code.

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190603065056.25211-9-peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Peter Xu 2019-06-03 14:50:53 +08:00 committed by Juan Quintela
parent 4a12a11a39
commit 9f4bf4baa8
2 changed files with 9 additions and 3 deletions
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10
accel/kvm/kvm-all.c
View File

@ -516,17 +516,19 @@ static int kvm_physical_sync_dirty_bitmap(KVMMemoryListener *kml,
*/
size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS),
/*HOST_LONG_BITS*/ 64) / 8;
d.dirty_bitmap = g_malloc0(size);
if (!mem->dirty_bmap) {
/* Allocate on the first log_sync, once and for all */
mem->dirty_bmap = g_malloc0(size);
}
d.dirty_bitmap = mem->dirty_bmap;
d.slot = mem->slot | (kml->as_id << 16);
if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) == -1) {
DPRINTF("ioctl failed %d\n", errno);
g_free(d.dirty_bitmap);
return -1;
}
kvm_get_dirty_pages_log_range(section, d.dirty_bitmap);
g_free(d.dirty_bitmap);
}
return 0;
@ -801,6 +803,8 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
}
/* unregister the slot */
g_free(mem->dirty_bmap);
mem->dirty_bmap = NULL;
mem->memory_size = 0;
mem->flags = 0;
err = kvm_set_user_memory_region(kml, mem, false);

2
include/sysemu/kvm_int.h
View File

@ -21,6 +21,8 @@ typedef struct KVMSlot
int slot;
int flags;
int old_flags;
/* Dirty bitmap cache for the slot */
unsigned long *dirty_bmap;
} KVMSlot;
typedef struct KVMMemoryListener {