RFC: top level compatibles for virtual platforms

[Grant Likely]

On Mon, Jul 11, 2011 at 11:34 PM, Yoder Stuart-B08248
<B08248 at freescale.com> wrote:
>
>
>> -----Original Message-----
>> From: Tabi Timur-B04825
>> Sent: Friday, July 08, 2011 8:39 PM
>> To: Yoder Stuart-B08248
>> Cc: Grant Likely; Benjamin Herrenschmidt; Gala Kumar-B11780; Wood Scott-B07421; Alexander
>> Graf; linuxppc-dev at ozlabs.org
>> Subject: Re: RFC: top level compatibles for virtual platforms
>>
>> On Fri, Jul 8, 2011 at 1:43 PM, Yoder Stuart-B08248 <B08248 at freescale.com> wrote:
>>
>> >   "MPC85xxDS" - for a virtual machine for the e500v2 type platforms
>> >                 and would support 85xx targets, plus P2020, P1022,etc
>> >
>> >   "corenet-32-ds" - for a virtual machine similar to the 32-bit P4080
>> >                     platforms
>> >
>> >   "corenet-64-ds" - for a virtual machine based on a 64-bit corenet
>> >                     platform
>>
>> I think we should drop the "DS" because that's a name applied to certain Freescale reference
>> boards.
>>
>> Is being a CoreNet board really something meaningful with respect to KVM?  I don't see the
>> connection.
>
> We're talking about what would be meaningful to Linux as a guest on
> this platform here--  Corenet-based SoCs are similar
> in various ways, like using msgsnd for IPIs, having external proxy
> support, etc.
>
> A corenet platform created by a QEMU/KVM looks similar
> to other corenet SoCs.   So, I'm trying to find some generic
> compatible string that describes this platform.
>
>> Also, if these are KVM creations, shouldn't there be a "kvm" in the compatible string
>> somewhere?
>
> There is nothing KVM specific about these platforms.  Any hypervisor
> could create a similar virtual machine.
>
> A guest OS can determine specific info about the hypervisor it is
> running on by looking at the /hypervisor node on the device
> tree.
>
> We could put a generic -hv extension to indicate that this is
> a virtual platform.
>
>  "mpc85xx-hv"
>  "corenet-32-hv"
>  "corenet-64-hv"

However, compatible values are cheap and while theoretically any
hypervisor could create a similar machine, the reality is probably
subtle difference between the implementations.  I'd rather see the
compatible reflect the specific implementation.

g.