Hi Ian,

On 01/30/2014 12:15 PM, Ian Campbell wrote:

On Thu, 2014-01-30 at 11:54 -0500, Christopher Covington wrote:

quoted

quoted

+++ b/Documentation/devicetree/bindings/arm/mach-virt.txt

@@ -0,0 +1,32 @@
+* Mach-virt "Dummy Virtual Machine" platform
+
+"mach-virt" is the smallest, dumbest platform possible, to be used as
+a guest for Xen, KVM and other hypervisors.

The platform is also useful to, and used by, simulators like QEMU in TCG mode.

I can mention this, although I don't think the list needs to be
exhaustive.

Cool, thanks. Agreed, but I thought it'd be nice to list the simulator class.

                                      It has no

quoted

quoted

+properties/functionality of its own and is driven entirely by device
+tree.

I find this wording confusing. I read it as saying the platform has no
properties or functionality. Perhaps you could phrase it slightly differently,
such as having no properties or functionality beyond what's described in the
device tree.

Yes, this is what I was trying to say, I'll update with something along
those lines.

quoted

quoted

+The platform may also provide hypervisor specific functionality
+(e.g. PV I/O), if it does so then this functionality must be
+discoverable (directly or indirectly) via device tree.

I think it would be informative to provide pointers here to commonly used
paravirtualized devices, especially VirtIO PCI/MMIO.

Under what criteria would something be eligible/appropriate to be
listed? I was trying to avoid "advocating" any particular type of PV
devices. We already have something of a problem with people incorrectly
assuming that mach-virt == virtio, which is not the case.

This isn't particularly scientific, but maybe a practical criteria could be
that it's mentioned in this thread? I think if we word the introduction to the
list clearly, readers will know that that these are just a few examples known
to be in use when the binding was written and by no means required. I think
that providing more information is more likely to fix the incorrect assumption
than providing less information.

If we did want to include an explicit list here at a minimum I would
also want to include the Xen PV devices as well and surely there would
be others which ought to be included too.

Yes, I assumed you would include Xen. I'm not aware of any others*, but
perhaps those who do could speak up about them?

(*I do use Angel semihosting and DCC from time to time, but I've never seen
devicetree bindings for these facilities. I'm not sure whether they count in
this context.)

Thanks,
Christopher

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