On 8/21/20 5:55 AM, Igor Mammedov wrote:
On Thu, 20 Aug 2020 12:51:03 -0400
Eduardo Habkost <ehabk...@redhat.com> wrote:
On Thu, Aug 20, 2020 at 02:15:04PM +1000, David Gibson wrote:
On Wed, Aug 19, 2020 at 10:11:28PM -0400, Eduardo Habkost wrote:
On Thu, Aug 20, 2020 at 11:17:26AM +1000, David Gibson wrote:
On Fri, Aug 14, 2020 at 05:54:16PM -0300, Daniel Henrique Barboza wrote:
The pSeries machine does not support asymmetrical NUMA
configurations.
This seems a bit oddly specific to have as a global machine class
property.
Would it make more sense for machines with specific NUMA constraints
to just verify those during their initialization?
This would be much simpler. However, I like the idea of
representing machine-specific configuration validation rules as
data that can eventually be exported to management software.
Ah, ok, so basically the usual tradeoff between flexibility and
advertisability.
So, in that case, I guess the question is whether we envisage "no
assymmetry" as a constraint common enough that it's worth creating an
advertisable rule or not. If we only ever have one user, then we
haven't really done any better than hard coding the constraint in the
manageent software.
Of course to complicate matters, in the longer term we're looking at
removing that constraint from pseries - but doing so will be dependent
on the guest kernel understanding a new format for the NUMA
information in the device tree. So qemu alone won't have enough
information to tell if such a configuration is possible or not.
Requiring both QEMU (and possibly management software) to be
patched again after the guest kernel is fixed sounds undesirable.
If we drop this restriction, then we don't need to touch QEMU when
guest kernel is ready.
Btw, what spapr spec says about the matter?
LOPAPR support a somewhat asymmetrical NUMA setup in its current form, but
the Linux kernel doesn't support it. The effort to implement it in the current
spapr machine code, given that Linux wouldn't mind it, is not worth it. This
is why I chose to invalidate it for pseries.
Perhaps a warning would be better in this case?
In either case, it sounds like this won't be a common constraint
and I now agree with your original suggestion of doing this in
machine initialization code.
Agreed, if it goes to spapr specific machine code I will not object much.
(it will burden just spapr maintainers, so it's about convincing
David in the end)
I believe he's ok with it given that he suggested it in his first reply.
I'll move this verification to spapr machine_init in the next version.
Thanks,
DHB
