Avi Kivity wrote:
Anthony Liguori wrote:
BTW, I don't think the target should be a config value. You don't
gain anything from it being in the config space and it's somewhat
unnatural for a virtio device. It makes more sense as a message to
the guest.
I disagree. The target is state, not an individual item that needs to
be acted on. Having it as a single variable means that multiple
changes are collapsed automatically, and that the the setting survives
module reload.
It's like a volume control, it doesn't send messages when you turn it,
it just sets a value.
It's a value that is meant to be acted upon though, not something to be
polled. You want to tell the driver that it should now try to balloon
to a certain value. Or maybe not. Maybe the driver should read the
target from the config space but then have a "kick" message that tells
it, hey, something's probably changed.
(maybe a thermostat knob is a better analogy, with the driver being
the circuitry around the knob that tries to control the temperature to
match the setting)
FWIW, I'm pretty sure that most modern volume controls are actually
button presses for either direction instead of a variable resistor but
point taken ;-)
I believe state-like controls will be useful for other settings, like
ethernet link state.
It's difficult with the current config interface since it treats
everything as a discrete blob that is updated all at once. I'm not
really sure how to proceed.
Rusty: do you have an opinion here?
Regards,
Anthony Liguori
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