Bug 444332

Summary: Allow 32-bit guests to be run on x86_64 with KVM
Product: [Fedora] Fedora Reporter: Geert Jansen <gjansen>
Component: libvirtAssignee: Daniel Veillard <veillard>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: high Docs Contact:
Priority: high    
Version: rawhideCC: berrange, bugzilla
Target Milestone: ---   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
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Clone Of: Environment:
Last Closed: 2008-04-27 12:02:03 EDT Type: ---
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Geert Jansen 2008-04-27 06:21:53 EDT
Description of problem:

Libvirt does not advertise that on x86_64 you can run 32-bit guests with the KVM
hypervisor. At the moment it only advertises QEMU which means you don't get the
improved performance of KVM.

Version-Release number of selected component (if applicable):

kvm-65-1.fc9.x86_64
libvirt-0.4.2-1.fc9.x86_64


How reproducible:

Always

Steps to Reproduce:

1. Install fresh F9 preview on a x86_64 system.
2. virsh -c qemu:///session capabilities 
3. The output above does not indicate that KVM can run 32-bit guests on x86_64.
  
Actual results:

The option of running 32-bit guests on a x86_64 system using KVM is not advertised.

Expected results:

KVM should be advertised as a way to run 32-bit guests on x86_64. Quoting the
KVM faq at http://kvm.qumranet.com/kvmwiki/FAQ:

4.11. Can kvm run a 32-bit guest on a 64-bit host? What about PAE?

kvm supports 32-bit guests on 64-bit hosts, and any combination of PAE and
non-PAE guests and hosts. The only unsupported combination is a 64-bit guest on
a 32-bit host.
Comment 1 Daniel Berrange 2008-04-27 12:02:03 EDT
The whole point of x86_64 is that it is compatible with i386 instruction set. ie
your 32-bit guest OS will run just fine in the x86_64 KVM vm. libvirt is
advertising the architecture of the virtual machine, not the architecture of the
OS to be run inside the virtual machine. As such it only advertises x86_64 on an
x86_64 host.
Comment 2 Geert Jansen 2008-04-27 12:06:32 EDT
You are right of course. The other options present in the list (i686, ...) made
me confuse. Sorry for the extra work caused.