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Subject: Re: [virtio-dev] Re: [PATCH v3 0/5] Support for datapath switching during live migration
On Mon, Jan 07, 2019 at 05:45:22PM -0800, si-wei liu wrote: > > > On 01/07/2019 03:32 PM, Michael S. Tsirkin wrote: > > 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*. > Why removing all status data from the event? To make sure users do not forget to call query-pci-master to re-enable more events. > It does not hurt to keep them > as the FAILOVER_PRIMARY_CHANGED event in general is of pretty low-frequency. A malicious guest can make it as frequent as it wants to. OTOH there is no way to limit. > As can be seen other similar low-frequent QMP events do have data carried > over. > > 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 OK if it's so important for latency let's include data in the event. Please add comments explaining that you must always re-run query afterwards to make sure it's stable and re-enable more events. > > > > > > 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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