Bug 502586
| Summary: | RHEL5.4: qemu-kvm should not fall back to TCG if KVM is not available | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 5 | Reporter: | Mark McLoughlin <markmc> |
| Component: | kvm | Assignee: | Eduardo Habkost <ehabkost> |
| Status: | CLOSED DUPLICATE | QA Contact: | Lawrence Lim <llim> |
| Severity: | medium | Docs Contact: | |
| Priority: | high | ||
| Version: | 5.4 | CC: | berrange, ovirt-maint, tburke, tools-bugs |
| Target Milestone: | rc | ||
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2009-05-27 09:07:50 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
IMHO disabling this is a bad idea - just consider the needs of libguestfs as one example. Its RPM build process runs KVM. The RHEL/Fedora mock/koji environment runs inside a virtual machine. Ergo, there is no hardware virt available during builds. So if we remove the fallback for TCG, it'll unnecessarily cause the builds to fail. Well, there's two issues:
1) What to do long term - the fallback will probably disappear as part of
merging KVM upstream things like libguestfs will have to explicitly
fall back themselves.
2) Whether we want to support TCG in 5.4 - IMHO, we don't and people who
want TCG (for whatever reason) should use qemu from EPEL
Alternative discussed solution is:
1) Move /usr/bin/qemu-kvm to /usr/libexec/qemu-kvm
2) Make /usr/bin/qemu-kvm a script which checks whether KVM is available
and and, if not, warns that TCG is not supported
Rationale is that TCG *is* needed for RHEV-M - apparently it uses qemu -no-kvm for some use cases
(In reply to comment #3) > Alternative discussed solution is: > > 1) Move /usr/bin/qemu-kvm to /usr/libexec/qemu-kvm > > 2) Make /usr/bin/qemu-kvm a script which checks whether KVM is available > and and, if not, warns that TCG is not supported > > Rationale is that TCG *is* needed for RHEV-M - apparently it uses qemu -no-kvm > for some use cases Since I have an open bug that should do exactly that + rhev-M needs -no-kvm mode I'm closing this bug. *** This bug has been marked as a duplicate of bug 489654 *** |
If you run qemu-kvm on a machine which doesn't support KVM, it will fallback to CPU emulation using TCG: $> mv /dev/kvm /dev/kvm.orig $> qemu-kvm -drive file=/var/lib/libvirt/images/test3.img -net none \ -monitor stdio -serial telnet::4444,server,nowait -nographic open /dev/kvm: No such file or directory Could not initialize KVM, will disable KVM support We don't want to support TCG, so we should disable this fallback. In theory, building with --disable-cpu-emulation does just that, but it doesn't build right now, even upstream.