KVM: PPC: Book3S HV: Set RWMR on POWER8 so PURR/SPURR count correctly

Although Linux doesn't use PURR and SPURR ((Scaled) Processor
Utilization of Resources Register), other OSes depend on them.
On POWER8 they count at a rate depending on whether the VCPU is
idle or running, the activity of the VCPU, and the value in the
RWMR (Region-Weighting Mode Register).  Hardware expects the
hypervisor to update the RWMR when a core is dispatched to reflect
the number of online VCPUs in the vcore.

This adds code to maintain a count in the vcore struct indicating
how many VCPUs are online.  In kvmppc_run_core we use that count
to set the RWMR register on POWER8.  If the core is split because
of a static or dynamic micro-threading mode, we use the value for
8 threads.  The RWMR value is not relevant when the host is
executing because Linux does not use the PURR or SPURR register,
so we don't bother saving and restoring the host value.

For the sake of old userspace which does not set the KVM_REG_PPC_ONLINE
register, we set online to 1 if it was 0 at the time of a KVM_RUN
ioctl.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index cb0f272ce123..44b2be4a65d1 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -365,6 +365,7 @@
 #define SPRN_PSSCR	0x357	/* Processor Stop Status and Control Register (ISA 3.0) */
 #define SPRN_PSSCR_PR	0x337	/* PSSCR ISA 3.0, privileged mode access */
 #define SPRN_PMCR	0x374	/* Power Management Control Register */
+#define SPRN_RWMR	0x375	/* Region-Weighting Mode Register */
 
 /* HFSCR and FSCR bit numbers are the same */
 #define FSCR_SCV_LG	12	/* Enable System Call Vectored */