Re: [libvirt] [RFC] exporting KVM host power saving capabilities through libvirt

On Tue, Jun 28, 2011 at 08:55:31PM +0530, Vaidyanathan Srinivasan wrote: > Hi, > > Linux host systems running KVM support various power management > capabilities. Most of the features like DVFS and sleep states can be > independently exploited by the host system itself based on system > utilisation subject to policies set by the administrator. > > However, system-wide low power states like S3 and S4 would require > external communication and interaction with the systems management > stack in order to be used. The first steps in this direction would be > to allow systems management stack to discover host power saving > capabilities like S3 and S4 along with various other host CPU > capabilities. > > Libvirt seems to be the main glue layer between the platform and the > systems-management stack. Adding host power savings capabilities as > part of libvirt host discovery mechanism seems to be one possible > approach without addition of any new APIs or agents. Can you provide the use cases you're looking to address with this work?

> libvirt has virConnectGetCapabilities() that would export an XML file > describing the capabilities of the host platform and guest features. > > KVM hypervisor's capability to support S3 can be exported as a host > feature in the XML as follows: > > <host> > <uuid>94a3492f-2635-2491-8c87-8de976fad119</uuid> > <cpu> > <arch>x86_64</arch> > <features> <<<=== New host feature fields > <S3/> > <S4/> > </features> Just my $.02, but calling it <features> seems to be confusingly close to the existing <feature> tag. Maybe <power_management> ? > <model>Westmere</model> > <vendor>Intel</vendor> > <topology sockets='1' cores='2' threads='2'/> > <feature name='rdtscp'/> > <feature name='xtpr'/> > <feature name='tm2'/> > <feature name='est'/> > <feature name='vmx'/> <<<= These are host CPU features > > System management software that works through libvirt, already queries > this capabilities XML file and hence no new API is needed. > > As simple discovery mechanism can be added to libvirt as follows: > > Index: libvirt-0.9.0/src/qemu/qemu_capabilities.c > =================================================================== > --- libvirt-0.9.0.orig/src/qemu/qemu_capabilities.c > +++ libvirt-0.9.0/src/qemu/qemu_capabilities.c > @@ -738,6 +738,14 @@ virCapsPtr qemuCapsInit(virCapsPtr old_c > virCapabilitiesAddHostMigrateTransport(caps, > "tcp"); > > + /* Add host energy management host capabilities */ > + > + /* if "pm-is-supported --suspend" == 0 */ > + virCapabilitiesAddHostFeature(caps, "S3"); > + > + /* if "pm-is-supported --hibernate" == 0 */ > + virCapabilitiesAddHostFeature(caps, "S4"); > + > /* First the pure HVM guests */ > for (i = 0 ; i < ARRAY_CARDINALITY(arch_info_hvm) ; i++) > if (qemuCapsInitGuest(caps, old_caps, > > > Please let me know your comments, I will code a working prototype > shortly and post for review/discussion. Dave -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list