Re: [virtio-dev] Re: [PATCH 0/5] virtio: introduce SUSPEND bit and vq state
"Zhu, Lingshan" <[email protected]>
| Newsgroups | dev.linux.lists.virtio-dev,dev.linux.lists.virtio-comment |
|---|---|
| Message-ID | <[email protected]> |
On 9/14/2023 7:37 PM, Michael S. Tsirkin wrote: > On Wed, Sep 06, 2023 at 04:16:32PM +0800, Zhu Lingshan wrote: >> This series introduces >> 1)a new SUSPEND bit in the device status >> Which is used to suspend the device, so that the device states >> and virtqueue states are stabilized. >> >> 2)virtqueue state and its accessor, to get and set last_avail_idx >> and last_used_idx of virtqueues. >> >> The main usecase of these new facilities is Live Migration. >> >> Future work: dirty page tracking and in-flight descriptors. >> >> This series addresses many comments from Jason, Stefan and Eugenio >> from RFC series. > > after going over this in detail, it is like I worried: this > tries to do too much through a single register and > the ownership is muddied significantly. Not sure about what ownership, device usually STOPPED after guest freezes, so the hypervisor owns the device status and LM facilities at that moment. > > I feel a separate capability for suspend/resume that would > be independent of device status would be preferable. The implementation of the live migration basic facilities are transport specific, for PCI: 1)Dirty page tracking will have its own capability 2)In-flight descriptors tracker will have its own capability 3)vq states stored in common config space Only SUSPEND is implemented in the device status, and this is a valid device status. There are already 6 device status bits, and IMHO this series implementing SUSPEND does not introduce more complexities. > >> Zhu Lingshan (5): >> virtio: introduce vq state as basic facility >> virtio: introduce SUSPEND bit in device status >> virtqueue: constraints for virtqueue state >> virtqueue: ignore resetting vqs when SUSPEND >> virtio-pci: implement VIRTIO_F_QUEUE_STATE >> >> content.tex | 118 ++++++++++++++++++++++++++++++++++++++++++++++ >> transport-pci.tex | 18 +++++++ >> 2 files changed, 136 insertions(+) >> >> -- >> 2.35.3 > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]