Re: [Qemu-devel] -cpu behavior (was: [PATCH v3 4/4] target-openrisc: Fix cpu_model by name)

["Andreas Färber" <afaerber@suse.de>]

Am 22.07.2013 17:38, schrieb Peter Maydell:
> On 22 July 2013 16:25, Anthony Liguori <anthony@codemonkey.ws> wrote:
>> Andreas Färber <afaerber@suse.de> writes:
>>> Am 22.07.2013 13:34, schrieb Peter Maydell:
>>>> Looking at all of the '-cpu help' output, alpha seems to be
>>>> the odd one out here: none of the others list valid CPUs
>>>> with "-$arch-cpu" suffixes.
>>>
>>> Right, because all others had implemented -cpu ? before we introduced
>>> that naming scheme and I tried to keep output compatibility for them.
>>> Focus for alpha was therefore on -cpu foo compatibility only.
>>>
>>> Anthony had clearly stated on a KVM call that using full type names for
>>> future CPU hot-add was the right thing to do and possibly even composite
>>> convenience types like 4core-xeonblabla-x86_64-cpu; how that relates to
>>> -cpu and new targets was never clearly defined though. ;)
>>
>> That's pretty gross, but yes, we should have:
>>
>> qemu -device Xeon-E5-4610,id=sock0 -device Xeon-E5-4610,id=sock1
>>
>> Which effectively does:
>>
>> qemu -cpu SandyBridge -smp cores=6,threads=2,sockets=2
>>
>> By today's standards.
> 
> That doesn't really answer the question of "should the argument
> to -cpu be a QOM typename or a human friendly name?" though
> (though I note none of your -cpu or -device argument examples
> are QOM type names, since they're missing the -$arch-cpu suffix).

Depending on how we register those types, they don't necessarily need an
-$arch-cpu suffix iff they are deemed globally unique. In this case
there would be a 32-bit and 64-bit type though, I guess.

But there's no qemu executable either, so we shouldn't take the example
literally. :P

>> I think this applies equally well to other architecture.
>>  Model hardware more closely.
> 
> For ARM this would mean "don't support -cpu at all, it
> is always hardwired by the board model" :-)

No, it means the board creates the equivalent of -device tegra2-soc. :)
Or exynos4210, highbank-soc or whatever. Less code in machine init, more
code in QOM devices reusable with -M none -readconfig foo.

Andreas

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