[libvirt] [PATCH] qemu: x86_64 is good enough for i686

[Daniel P. Berrange]

On Tue, Oct 21, 2014 at 01:33:00PM +0200, Martin Kletzander wrote:
> On Thu, Oct 16, 2014 at 09:28:00PM +0200, Lubomir Rintel wrote:
> >virt-manager on Fedora sets up i686 hosts with "/usr/bin/qemu-kvm" emulator,
> >which in turn unconditionally execs qemu-system-x86_64 querying capabilities
> >then fails:
> >
> >Error launching details: invalid argument: architecture from emulator 'x86_64' doesn't match given architecture 'i686'
> >
> >Traceback (most recent call last):
> > File "/usr/share/virt-manager/virtManager/engine.py", line 748, in _show_vm_helper
> >   details = self._get_details_dialog(uri, vm.get_connkey())
> > File "/usr/share/virt-manager/virtManager/engine.py", line 726, in _get_details_dialog
> >   obj = vmmDetails(conn.get_vm(connkey))
> > File "/usr/share/virt-manager/virtManager/details.py", line 399, in __init__
> >   self.init_details()
> > File "/usr/share/virt-manager/virtManager/details.py", line 784, in init_details
> >   domcaps = self.vm.get_domain_capabilities()
> > File "/usr/share/virt-manager/virtManager/domain.py", line 518, in get_domain_capabilities
> >   self.get_xmlobj().os.machine, self.get_xmlobj().type)
> > File "/usr/lib/python2.7/site-packages/libvirt.py", line 3492, in getDomainCapabilities
> >   if ret is None: raise libvirtError ('virConnectGetDomainCapabilities() failed', conn=self)
> >libvirtError: invalid argument: architecture from emulator 'x86_64' doesn't match given architecture 'i686'
> >
> >Journal:
> >
> >Oct 16 21:08:26 goatlord.localdomain libvirtd[1530]: invalid argument: architecture from emulator 'x86_64' doesn't match given architecture 'i686'
> >---
> >src/qemu/qemu_driver.c | 3 ++-
> >1 file changed, 2 insertions(+), 1 deletion(-)
> >
> >diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> >index 7377320..e4b2b6c 100644
> >--- a/src/qemu/qemu_driver.c
> >+++ b/src/qemu/qemu_driver.c
> >@@ -17809,7 +17809,8 @@ qemuConnectGetDomainCapabilities(virConnectPtr conn,
> >
> >        arch_from_caps = virQEMUCapsGetArch(qemuCaps);
> >
> >-        if (arch_from_caps != arch) {
> >+        if (arch_from_caps != arch &&
> >+	    (arch_from_caps != VIR_ARCH_X86_64 || arch != VIR_ARCH_I686)) {
> 
> You haven't ran make syntax-check, otherwise it would tell you there's
> tab with 4 spaces after that and we use spaces only.
> 
> It would be nice to add a test case for this particular case.  Anyway
> ACK, I'll push it in a while with that line fixed.
> 
> However, I wonder if we only limit the 32/64 bit machines by the
> processor, because it looks like one can run even the following
> combination:
> 
>  qemu-system-i686 -cpu Haswell
> 
> And this is even with <type arch='x86_64' machine='pc-q35-2.2'>!  Is
> this still 64bit cpu running in 32bit mode?

If libvirt / qemu allows you to request <type arch=x86_64> when pointing
<emulator> to the i686 system emulator binary that is a bug IMHO. We
should reject nonsensical combinations like that.

Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|