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authorDavid Gibson <david@gibson.dropbear.id.au>2011-04-01 15:15:33 +1100
committerAlexander Graf <agraf@suse.de>2011-04-01 18:34:57 +0200
commited120055c7f9b26b5707d3ceabbe5a3f06aaf937 (patch)
tree4c76031ec0bbf527e0de0a4bec2f635dd598aa56 /sysconfigs/target
parent08942ac17922d923a7cc5cf9854e9cc4b150b942 (diff)
Implement PAPR VPA functions for pSeries shared processor partitions
Shared-processor partitions are those where a CPU is time-sliced between partitions, rather than being permanently dedicated to a single partition. qemu emulated partitions, since they are just scheduled with the qemu user process, behave mostly like shared processor partitions. In order to better support shared processor partitions (splpar), PAPR defines the "VPA" (Virtual Processor Area), a shared memory communication channel between the hypervisor and partitions. There are also two additional shared memory communication areas for specialized purposes associated with the VPA. A VPA is not essential for operating an splpar, though it can be necessary for obtaining accurate performance measurements in the presence of runtime partition switching. Most importantly, however, the VPA is a prerequisite for PAPR's H_CEDE, hypercall, which allows a partition OS to give up it's shared processor timeslices to other partitions when idle. This patch implements the VPA and H_CEDE hypercalls in qemu. We don't implement any of the more advanced statistics which can be communicated through the VPA. However, this is enough to make normal pSeries kernels do an effective power-save idle on an emulated pSeries, significantly reducing the host load of a qemu emulated pSeries running an idle guest OS. Signed-off-by: David Gibson <dwg@au1.ibm.com> Signed-off-by: Alexander Graf <agraf@suse.de>
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