Re: [Xen-devel] [BUG?] qemuu only built with i386-softmmu

[Steven Haigh <netwiz@xxxxxxxxx>]

On 05/02/16 20:51, Ian Campbell wrote:
> On Fri, 2016-02-05 at 08:09 +1100, Steven Haigh wrote:
>> In building my Xen 4.6.0 packages, I disable qemu-traditional and ONLY
>> build qemu-upstream - however as the value for i386-softmmu is not based
>> on variables, I'm not sure this makes a difference.
> 
> QEMU in a Xen system only provides device model (DM) emulation and not any
> CPU instruction emulation, so the nominal arch doesn't actually matter and
> Xen build's i386 everywhere as a basically arbitrary choice.
> 
> It happens that the Xen DM part of QEMU is quite closely tied to the x86
> scaffolding for various historical reasons, so we end up using qemu-system-
> i386 even e.g. on ARM!
> 
> This comes up a lot, So I've also pasted the two paras above into a new
> section in http://wiki.xenproject.org/wiki/QEMU_Upstream . If anyone thinks
> the above is inaccurate then please edit the wiki (and post here too if you
> like).

I think this is a great addition that explains the situation well.
Documenting these is always a good thing.

> 
> On thing I was sure on (so didn't write) is whether the second paragraph
> could have an extra sentence:
> 
>     If you are using a distro supplied QEMU then the qemu-system-x86_64
>     could also be used, but it makes no practical difference to the
>     functionality of the system.
> 
> I wasn't sure if that was true (I suspect it is) and in any case I think
> various bits of libxl etc will look for qemu-system-i386 in various paths
> so a user would need to try reasonably hard to do so by giving an explicit
> path and there is no real reason to do so maybe better not to muddy the
> waters?

Maybe go along the lines of:

"There is no practical difference between qemu-system-i386 and
qemu-system-x86_64 therefore both can be interchanged freely."

-- 
Steven Haigh

Email: netwiz@xxxxxxxxx
Web: https://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897

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