On Wed, Aug 27, 2014 at 01:53:21PM +0200, Michael S. Tsirkin wrote:
> On Tue, Aug 26, 2014 at 04:06:17PM +0800, zhanghailiang wrote:
> > For all NICs(except virtio-net) emulated by qemu,
> > Such as e1000, rtl8139, pcnet and ne2k_pci,
> > Qemu can still receive packets when VM is not running.
> >
> > If this happened in *migration's* last PAUSE VM stage, but
> > before the end of the migration, the new receiving packets will possibly
> > dirty
> > parts of RAM which has been cached in *iovec*(will be sent asynchronously)
> > and
> > dirty parts of new RAM which will be missed.
> > This will lead serious network fault in VM.
> >
> > To avoid this, we forbid receiving packets in generic net code when
> > VM is not running.
> >
> > Bug reproduction steps:
> > (1) Start a VM which configured at least one NIC
> > (2) In VM, open several Terminal and do *Ping IP -i 0.1*
> > (3) Migrate the VM repeatedly between two Hosts
> > And the *PING* command in VM will very likely fail with message:
> > 'Destination HOST Unreachable', the NIC in VM will stay unavailable unless
> > you
> > run 'service network restart'
> >
> > Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
>
> Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
Please add:
Cc: qemu-sta...@nongnu.org
when applying this.
Thanks!
> > ---
> > v4:
> > - The action of flush queued packets is unnecessary, remove this.
> > (Thanks for the help of Jason Wang and Stefan).
> >
> > v3:
> > - change the 'vmstate' to 'vm_running'
> >
> > v2:
> > - remove the superfluous check of nc->received_disabled
> > ---
> >
> > net/net.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/net/net.c b/net/net.c
> > index 6d930ea..4cb92c0 100644
> > --- a/net/net.c
> > +++ b/net/net.c
> > @@ -41,6 +41,7 @@
> > #include "qapi-visit.h"
> > #include "qapi/opts-visitor.h"
> > #include "qapi/dealloc-visitor.h"
> > +#include "sysemu/sysemu.h"
> >
> > /* Net bridge is currently not supported for W32. */
> > #if !defined(_WIN32)
> > @@ -452,6 +453,12 @@ void qemu_set_vnet_hdr_len(NetClientState *nc, int len)
> >
> > int qemu_can_send_packet(NetClientState *sender)
> > {
> > + int vm_running = runstate_is_running();
> > +
> > + if (!vm_running) {
> > + return 0;
> > + }
> > +
> > if (!sender->peer) {
> > return 1;
> > }
> > --
> > 1.7.12.4
> >
