On Tue, 2020-03-24 at 11:05 -0300, Daniel Henrique Barboza wrote:
On 3/24/20 11:00 AM, Andrea Bolognani wrote:
On Tue, 2020-03-24 at 09:27 -0300, Daniel Henrique Barboza wrote:
For the sake of completeness, I'll also mention that we can simply allow <pmu/> to be declared in the XML, handling the <pmu state='on'/> inside the QEMU driver to not add the bogus '.pmu' parameter for QEMU ppc64, forbid <pmu state='off'/> to be declared, and nothing else. No auto-generation of XML indicating that the guest will support a PMU.
Looking again at how other architectures, specifically x86 and ARM, handle this, the PMU is generally enabled by default without this fact being reflected in the domain XML; the user can then go ahead and specifically ask for it to be turned on or off, at which point libvirt will add the relevant bits to the QEMU command line.
This is basically the second behavior you're describing above, and I think it would be perfectly fine if that's the one we would adopt for ppc64.
I guess I'll roll with this one then. I will allow <pmu state='on'/> to be declared in the XML without breaking QEMU. For <pmu state='off'/> I'll throw an CONFIG_UNSUPPORTED error mentioning that PMU can't be turned off for ppc64.
Sounds good. -- Andrea Bolognani / Red Hat / Virtualization