Quoting Michael Tokarev (m...@tls.msk.ru): > 09.04.2014 07:21, Serge Hallyn wrote: > > ENOENT (iiuc) means the kernel has an empty dirty bitmap for this > > slot. Don't abort in that case. This appears to solve the bug > > reported at > > > > https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1303926 > > > > which first showed up with commit b533f658a98325d: fix return check for > > KVM_GET_DIRTY_LOG ioctl > > > > Signed-off-by: Serge Hallyn <serge.hal...@ubuntu.com> > > --- > > kvm-all.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/kvm-all.c b/kvm-all.c > > index 82a9119..7b7ea8d 100644 > > --- a/kvm-all.c > > +++ b/kvm-all.c > > @@ -441,10 +441,13 @@ static int > > kvm_physical_sync_dirty_bitmap(MemoryRegionSection *section) > > > > d.slot = mem->slot; > > > > - if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) == -1) { > > + ret = kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d); > > + if (ret < 0 && ret != -ENOENT) { > > DPRINTF("ioctl failed %d\n", errno); > > ret = -1; > > break; > > + } else if (ret < 0) { > > + ret = 0; > > } > > > > kvm_get_dirty_pages_log_range(section, d.dirty_bitmap); > > Should we omit calling kvm_get_dirty_pages_log_range() if there's > no bitmap from kernel?
If that's something we can know then certainly that'll be better. It'll save an ioctl and copy_from_user of the whole of &d. > In particular, do we trust kernel to not > touch d.dirty_bitmap when it returns ENOENT? Seems ok, kvm_vm_ioctl_get_dirty_log() doesn't change anything in *log before returning when it finds no dirty_mapslot. -serge
