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Subject: Re: [PATCH] virtio-transport: Clarify requirements
Cornelia Huck <cohuck@redhat.com> writes: > On Wed, Dec 06 2023, Viresh Kumar <viresh.kumar@linaro.org> wrote: > >> On 05-12-23, 14:18, Cornelia Huck wrote: >>> On Tue, Dec 05 2023, Viresh Kumar <viresh.kumar@linaro.org> wrote: <snip> >> >> - The transport MUST provide a mechanism for the device and the driver >> to notify each other, for example about availability of a buffer on >> the virtqueue. > > Probably a mechanism for the device to notify the driver, and a > mechanism for the driver to notify the device? They can be different, as > long both of them are present. > >> >> - The transport SHOULD provide a mechanism for the driver to initiate >> a reset of the virtqueues and device. > > Can we mandate a mechanism for a device reset? Reset of virtqueues needs > to be optional, I'm not sure whether a SHOULD would be appropriate for > that (or maybe we should finally come up with something for ccw ;) > > Other things that probably should be mandatory: > > - A way for the driver to change the device status. Reading it would > probably be a strong SHOULD. > - A way to implement config space. (For example, channel devices don't > have a config space or anything similar enough to repurpose, so I had > to invent a mechanism for ccw... maybe future transports will be in > the same boat.) I think Bill has run into problems with config space on OpenAMP setups where there can be no specific trapping between domains making it hard to manage a config space where both sides might want to make updates. I guess the original MMIO transport gets away with it because config space is always in the trap-and-emulate address space in a normal VM/emulation situation. Bill, Is the plan to introduce a new transport that manages config in a different way? -- Alex BennÃe Virtualisation Tech Lead @ Linaro
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