In v6.0.0-rc1~439 (and friends) we tried to cache NUMA capabilities because we assumed they are immutable. And to some extent they are (NUMA hotplug is not a thing, is it). However, our capabilities contain also some runtime info that can change, e.g. hugepages pool allocation sizes or total amount of memory per node (host side memory hotplug might change the value). When rebuilding virCaps (e.g. for 'virsh capabilities') we have to dropped the cached info and rebuild it from scratch so that the correct runtime info is reported. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1819058 Fixes: 1a1d848694f6c2f1d98a371124928375bc3bb4a3 Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- After this, we are still caching CPU caps, but I'm not sure if that is a problem. Perhaps if CPU was hotplugged/unplugged? I don't know. src/qemu/qemu_conf.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c index d6615ca0dd..89a16349bf 100644 --- a/src/qemu/qemu_conf.c +++ b/src/qemu/qemu_conf.c @@ -1380,6 +1380,12 @@ virCapsPtr virQEMUDriverCreateCapabilities(virQEMUDriverPtr driver) "DOI \"%s\"", model, doi); } + /* Forcibly recreate NUMA caps. They are not static + * (e.g. size of hugepages pools can change). */ + qemuDriverLock(driver); + g_clear_pointer(&driver->hostnuma, virCapabilitiesHostNUMAUnref); + qemuDriverUnlock(driver);

On Tue, Dec 01, 2020 at 13:54:29 +0100, Michal Privoznik wrote: > In v6.0.0-rc1~439 (and friends) we tried to cache NUMA > capabilities because we assumed they are immutable. And to some > extent they are (NUMA hotplug is not a thing, is it). However, > our capabilities contain also some runtime info that can change, > e.g. hugepages pool allocation sizes or total amount of memory > per node (host side memory hotplug might change the value). > > When rebuilding virCaps (e.g. for 'virsh capabilities') we have > to dropped the cached info and rebuild it from scratch so that > the correct runtime info is reported. > > Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1819058 > Fixes: 1a1d848694f6c2f1d98a371124928375bc3bb4a3 > Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; > --- > > After this, we are still caching CPU caps, but I'm not sure if that is a > problem. Perhaps if CPU was hotplugged/unplugged? I don't know. > > src/qemu/qemu_conf.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c > index d6615ca0dd..89a16349bf 100644 > --- a/src/qemu/qemu_conf.c > +++ b/src/qemu/qemu_conf.c > @@ -1380,6 +1380,12 @@ virCapsPtr virQEMUDriverCreateCapabilities(virQEMUDriverPtr driver) > "DOI \"%s\"", model, doi); > } > > + /* Forcibly recreate NUMA caps. They are not static > + * (e.g. size of hugepages pools can change). */ > + qemuDriverLock(driver); > + g_clear_pointer(&driver->hostnuma, virCapabilitiesHostNUMAUnref); > + qemuDriverUnlock(driver); On a second look, this looks really fishy here. virQEMUDriverCreateCapabilities is meant to convert 'driver' internals into a virCaps. It has no business modifying 'driver'.

> + > caps->host.numa = virQEMUDriverGetHostNUMACaps(driver); If we always require new numa data, why don't we fetch it here instead of having the driver code generate it? Also if it needs to be refreshed on use, maybe caching it is not the best approach in the first place.