On Thu, 25 Jul 2024 14:50:50 +0100 David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > On Thu, 2024-07-25 at 08:33 -0400, Michael S. Tsirkin wrote: > > On Thu, Jul 25, 2024 at 01:31:19PM +0100, David Woodhouse wrote: > > > On Thu, 2024-07-25 at 08:29 -0400, Michael S. Tsirkin wrote: > > > > On Thu, Jul 25, 2024 at 01:27:49PM +0100, David Woodhouse wrote: > > > > > On Thu, 2024-07-25 at 08:17 -0400, Michael S. Tsirkin wrote: > > > > > > On Thu, Jul 25, 2024 at 10:56:05AM +0100, David Woodhouse wrote: > > > > > > > > Do you want to just help complete virtio-rtc then? Would be easier than > > > > > > > > trying to keep two specs in sync. > > > > > > > > > > > > > > The ACPI version is much more lightweight and doesn't take up a > > > > > > > valuable PCI slot#. (I know, you can do virtio without PCI but that's > > > > > > > complex in other ways). > > > > > > > > > > > > > > > > > > > Hmm, should we support virtio over ACPI? Just asking. > > > > > > > > > > Given that we support virtio DT bindings, and the ACPI "PRP0001" device > > > > > exists with a DSM method which literally returns DT properties, > > > > > including such properties as "compatible=virtio,mmio" ... do we > > > > > already? > > > > > > > > > > > > > > > > > > In a sense, but you are saying that is too complex? > > > > Can you elaborate? > > > > > > No, I think it's fine. I encourage the use of the PRP0001 device to > > > expose DT devices through ACPI. I was just reminding you of its > > > existence. > > > > Confused. You said "I know, you can do virtio without PCI but that's > > complex in other ways" as the explanation why you are doing a custom > > protocol. > > Ah, apologies, I wasn't thinking that far back in the conversation. > > If we wanted to support virtio over ACPI, I think PRP0001 can be made > to work and isn't too complex (even though it probably doesn't yet work > out of the box). > > But for the VMCLOCK thing, yes, the simple ACPI device is a lot simpler > than virtio-rtc and much more attractive. > > Even if the virtio-rtc specification were official today, and I was > able to expose it via PCI, I probably wouldn't do it that way. There's > just far more in virtio-rtc than we need; the simple shared memory > region is perfectly sufficient for most needs, and especially ours. > > I have reworked > https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/vmclock > to take your other feedback into account. > > It's now more flexible about the size handling, and explicitly checking > that specific fields are present before using them. > > I think I'm going to add a method on the ACPI device to enable the > precise clock information. I haven't done that in the driver yet; it > still just consumes the precise clock information if it happens to be > present already. The enable method can be added in a compatible fashion > (the failure mode is that guests which don't invoke this method when > the hypervisor needs them to will see only the disruption signal and > not precise time). > > For the HID I'm going to use AMZNVCLK. I had used QEMUVCLK in the QEMU > patches, but I'll change that to use AMZNVCLK too when I repost the > QEMU patch. That doesn't fit with ACPI _HID definitions. Second set 4 characters need to be hex digits as this is an ACPI style ID (which I assume this is given AMZN is a valid vendor ID. 6.1.5 in ACPI v6.5 Maybe I'm missing something... J
