On 26 July 2024 17:49:58 BST, Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote: >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 > > Hm, is the same not true for QEMUVGID and AMZNVGID, which I was using as an example? QEMU seemed to get to 0002, and AFAICT the VMGENID patches were initially posted using QEMU0003, but what's actually in QEMU now is QEMUVGID. So I presumed that was now the preferred option.
