From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Samudrala, Sridhar" Subject: Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net Date: Tue, 5 Jun 2018 13:20:33 -0700 Message-ID: <0a69d897-d084-8a7e-a681-86a49ab8f59a@intel.com> References: <1525734594-11134-1-git-send-email-sridhar.samudrala@intel.com> <20180605152344-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180605152344-mutt-send-email-mst@kernel.org> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" Cc: alexander.h.duyck@intel.com, virtio-dev@lists.oasis-open.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On 6/5/2018 5:33 AM, Michael S. Tsirkin wrote: > I don't think this is sufficient. Sure. This is not sufficient for a complete solution, but is Qemu the right place to manage primary/standby interfaces? I think the other steps including plugging/unplugging the primary interface needs to handled by some orchestration layer. > > If both primary and standby devices are present, a legacy guest without > support for the feature might see two devices with same mac and get > confused. Yes. Isn't this possible today when a VM is started with a mis-configured domain XML file that passes a virtio-net interface and a VF with the same MAC? > > I think that we should only make primary visible after guest acked the > backup feature bit. The primary can be plugged/unplugged at any time by the management layer. So i guess this needs to be handled in the libvirt layer. > > And on reset or when backup is cleared in some other way, unplug the > primary. > > Something like the below will do the job: > > Primary device is added with a special "primary-failover" flag. Are you suggesting an extension to Qemu to add another flag for primary device too? > A virtual machine is then initialized with just a standby virtio > device. Primary is not yet added. > > Later QEMU detects that guest driver device set DRIVER_OK. > It then exposes the primary device to the guest, and triggers > a device addition event (hot-plug event) for it. > > If QEMU detects guest driver removal, it initiates a hot-unplug sequence > to remove the primary driver. In particular, if QEMU detects guest > re-initialization (e.g. by detecting guest reset) it immediately removes > the primary device. > > We can move some of this code to management as well, architecturally it > does not make too much sense but it might be easier implementation-wise. > > HTH > > On Mon, Jun 04, 2018 at 06:41:48PM -0700, Samudrala, Sridhar wrote: >> Ping on this patch now that the kernel patches are accepted into davem's net-next tree. >> https://patchwork.ozlabs.org/cover/920005/ >> >> >> On 5/7/2018 4:09 PM, Sridhar Samudrala wrote: >>> This feature bit can be used by hypervisor to indicate virtio_net device to >>> act as a standby for another device with the same MAC address. >>> >>> I tested this with a small change to the patch to mark the STANDBY feature 'true' >>> by default as i am using libvirt to start the VMs. >>> Is there a way to pass the newly added feature bit 'standby' to qemu via libvirt >>> XML file? >>> >>> Signed-off-by: Sridhar Samudrala >>> --- >>> hw/net/virtio-net.c | 2 ++ >>> include/standard-headers/linux/virtio_net.h | 3 +++ >>> 2 files changed, 5 insertions(+) >>> >>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c >>> index 90502fca7c..38b3140670 100644 >>> --- a/hw/net/virtio-net.c >>> +++ b/hw/net/virtio-net.c >>> @@ -2198,6 +2198,8 @@ static Property virtio_net_properties[] = { >>> true), >>> DEFINE_PROP_INT32("speed", VirtIONet, net_conf.speed, SPEED_UNKNOWN), >>> DEFINE_PROP_STRING("duplex", VirtIONet, net_conf.duplex_str), >>> + DEFINE_PROP_BIT64("standby", VirtIONet, host_features, VIRTIO_NET_F_STANDBY, >>> + false), >>> DEFINE_PROP_END_OF_LIST(), >>> }; >>> diff --git a/include/standard-headers/linux/virtio_net.h b/include/standard-headers/linux/virtio_net.h >>> index e9f255ea3f..01ec09684c 100644 >>> --- a/include/standard-headers/linux/virtio_net.h >>> +++ b/include/standard-headers/linux/virtio_net.h >>> @@ -57,6 +57,9 @@ >>> * Steering */ >>> #define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */ >>> +#define VIRTIO_NET_F_STANDBY 62 /* Act as standby for another device >>> + * with the same MAC. >>> + */ >>> #define VIRTIO_NET_F_SPEED_DUPLEX 63 /* Device set linkspeed and duplex */ >>> #ifndef VIRTIO_NET_NO_LEGACY