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