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Subject: Re: [virtio] [OASIS Issue Tracker] Updated: (VIRTIO-11) Method to stop activity on a queue?
On Fri, 25 Oct 2013 13:16:01 +1030 Rusty Russell <rusty@au1.ibm.com> wrote: > OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org> writes: > > [ http://tools.oasis-open.org/issues/browse/VIRTIO-11?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] > > > > Rusty Russell updated VIRTIO-11: > > -------------------------------- > > > > Description: > > This has been requested for network devices before. > > > > In particular, in Linux when a network device is closed we leave the buffers in the receive queue, since we can't remove them without resetting the device. > > > > was:This has been requested for network devices before. Sometimes it would be useful to stop all queue activity; for example this would allow the driver to stop queue, process any pending interrupts, then pull buffers out of the queue. > > > > > > This is now available in the draft for PCI. > > And it could be done for MMIO by setting QueuePFN to zero, though the > spec should specify that as allowed on a live device. > > I'm not sure the best way to add this functionality to CCW. Cornelia? I'm not quite sure what the requirements are here. - Allow the guest to deregister a single vq? The SET_VQ command should be able to do that; we would need to make it amply clear that this can be done in-flight, though. - Allow the guest to tell the host to leave a queue alone for a time? The best approach for that would probably be a new command (or a hypercall) passing a queue-active mask; this would allow the guest to re-enable queue usage later on. - Or the reverse: Allow the host to temporarily halt processing. Probably with unsolicited interrupts indicating a state change, similar to what storage servers do. This would be per-device, however. > > Cheers, > Rusty.
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