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Subject: Re: [virtio-dev] Re: [PATCH v3 0/5] Support for datapath switching during live migration
On 01/07/2019 03:32 PM, Michael S. Tsirkin wrote:
Why removing all status data from the event? It does not hurt to keep them as the FAILOVER_PRIMARY_CHANGED event in general is of pretty low-frequency. As can be seen other similar low-frequent QMP events do have data carried over.On Mon, Jan 07, 2019 at 05:29:39PM -0500, Venu Busireddy wrote:Implement the infrastructure to support datapath switching during live migration involving SR-IOV devices. 1. This patch is based off on the current VIRTIO_NET_F_STANDBY feature bit and MAC address device pairing. 2. This set of events will be consumed by userspace management software to orchestrate all the hot plug and datapath switching activities. This scheme has the least QEMU modifications while allowing userspace software to build its own intelligence to control the whole process of SR-IOV live migration. 3. While the hidden device model (viz. coupled device model) is still being explored for automatic hot plugging (QEMU) and automatic datapath switching (host-kernel), this series provides a supplemental set of interfaces if management software wants to drive the SR-IOV live migration on its own. It should not conflict with the hidden device model but just offers simplicity of implementation. Si-Wei Liu (2): vfio-pci: Add FAILOVER_PRIMARY_CHANGED event to shorten downtime during failover pci: query command extension to check the bus master enabling status of the failover-primary device Sridhar Samudrala (1): virtio_net: Add VIRTIO_NET_F_STANDBY feature bit. Venu Busireddy (2): virtio_net: Add support for "Data Path Switching" during Live Migration. virtio_net: Add a query command for FAILOVER_STANDBY_CHANGED event. --- Changes in v3: Fix issues with coding style in patch 3/5. Changes in v2: Added a query command for FAILOVER_STANDBY_CHANGED event. Added a query command for FAILOVER_PRIMARY_CHANGED event.Hmm it looks like all feedback I sent e.g. here: https://patchwork.kernel.org/patch/10721571/ got ignored. To summarize I suggest reworking the series adding a new command along the lines of (naming is up to you): query-pci-master - this returns status for a device and enables a *single* event after it changes and then removing all status data from the event, just notify about the change and *only once*.
As this event relates to datapath switching, there's implication to coalesce events as packets might not get a chance to send out as nothing would ever happen when going through quick transitions like disabled->enabled->disabled. I would allow at least few packets to be sent over wire rather than nothing. Who knows how fast management can react and consume these events?
Thanks, -Siwei
upon event management does query-pci-master and acts accordingly.hmp.c | 5 +++ hw/acpi/pcihp.c | 27 +++++++++++ hw/net/virtio-net.c | 42 +++++++++++++++++ hw/pci/pci.c | 5 +++ hw/vfio/pci.c | 60 +++++++++++++++++++++++++ hw/vfio/pci.h | 1 + include/hw/pci/pci.h | 1 + include/hw/virtio/virtio-net.h | 1 + include/net/net.h | 2 + net/net.c | 61 +++++++++++++++++++++++++ qapi/misc.json | 5 ++- qapi/net.json | 100 +++++++++++++++++++++++++++++++++++++++++ 12 files changed, 309 insertions(+), 1 deletion(-)--------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
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