On Mon, May 25, 2020 at 09:39:45 -0300, Daniel Henrique Barboza wrote:
Commit v3.10.0-182-g237f045d9a ("qemu: Ignore fallback CPU attribute on reconnect") forced CPU 'fallback' to ALLOW, regardless of user choice. This fixed a situation in which guests created with older Libvirt versions, which used CPU mode 'host-model' in runtime, would fail to launch in a newer Libvirt if the fallback was set to FORBID. This would lead to a scenario where the CPU was translated to 'host-model' to 'custom', but then the FORBID setting would make the translation process fail.
PSeries can operate with 'host-model' in runtime due to specific PPC64 mechanics regarding compatibility mode. The update() implementation of the cpuDriverPPC64 driver is a NO-OP if CPU mode is 'host-model', and the driver does not implement translate(). The commit mentioned above is causing PSeries guests to get their 'fallback' setting to ALLOW, overwriting user choice, exposing a design problem in qemuProcessRefreshCPU() - for PSeries guests, handling 'host-model' as it is being done does not apply.
All other cpuArchDrivers implements update() and changes guest mode to VIR_CPU_MODE_CUSTOM, meaning that PSeries is currently the only exception to this logic. Let's make it official.
https://bugzilla.redhat.com/show_bug.cgi?id=1660711
Suggested-by: Jiri Denemark <jdenemar@redhat.com> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> --- src/qemu/qemu_process.c | 9 +++++++++ 1 file changed, 9 insertions(+)
Reviewed-by: Jiri Denemark <jdenemar@redhat.com> Thanks and pushed.