| Message ID | 20140409032106.GA5163@sergelap |
|---|---|
| State | New |
| Headers | show |
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.hallyn@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? In particular, do we trust kernel to not touch d.dirty_bitmap when it returns ENOENT? Thanks, /mjt
Quoting Michael Tokarev (mjt@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.hallyn@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
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);
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.hallyn@ubuntu.com> --- kvm-all.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)