From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42221) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XMbmq-00033c-J9 for qemu-devel@nongnu.org; Wed, 27 Aug 2014 07:53:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XMbmj-0001cv-AT for qemu-devel@nongnu.org; Wed, 27 Aug 2014 07:53:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36152) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XMbmj-0001cm-3a for qemu-devel@nongnu.org; Wed, 27 Aug 2014 07:53:05 -0400 Date: Wed, 27 Aug 2014 13:53:21 +0200 From: "Michael S. Tsirkin" Message-ID: <20140827115321.GB16850@redhat.com> References: <1409040377-12088-1-git-send-email-zhang.zhanghailiang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1409040377-12088-1-git-send-email-zhang.zhanghailiang@huawei.com> Subject: Re: [Qemu-devel] [PATCH V4] net: Forbid dealing with packets when VM is not running List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: zhanghailiang Cc: aliguori@amazon.com, jasowang@redhat.com, luonengjun@huawei.com, peter.huangpeng@huawei.com, qemu-devel@nongnu.org, stefanha@redhat.com 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 Reviewed-by: Michael S. Tsirkin > --- > 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 >