Commit 9f4bf4ba authored by Peter Xu's avatar Peter Xu Committed by Juan Quintela
Browse files

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: default avatarPeter Xu <peterx@redhat.com>
Reviewed-by: default avatarJuan Quintela <quintela@redhat.com>
Reviewed-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190603065056.25211-9-peterx@redhat.com>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com>
parent 4a12a11a

accel/kvm/kvm-all.c

+7 −3
Original line number Diff line number Diff line
@@ -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);

include/sysemu/kvm_int.h

+2 −0
Original line number Diff line number Diff line
@@ -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 {