[PATCH 0/2] Increase number of supported IPI messages

[Suresh Warrier]

When a H_IPI hypercall is made, we often need to switch to the 
host to poke the VCPU to which the virtual IPI is targeted. 
This is because we cannot do a thread wake-up in real mode in 
the guest. Peformance tests have shown that this is impacting
several different workloads - from MongoDB to small message
networking.

One solution is to hand off this job of waking the VCPU to a CPU
that is running in the host by sending it a message through the 
IPI mechanism from the guest. 

Currently, we only support 4 IPI messages and all 4 are already 
used for other purposes. This patch set increases the number
of supported IPI messages to 8. It also provides the code to
send an IPI from KVM real-mode since the existing cause_ipi
functions cannot be executed in real-mode.

There is an associated patch set for "KVM: PPC: Book3S HV" 
that implements the actual solution to avoid the switch to
host to do the VCPU wakeup. 

Suresh Warrier (2):
  powerpc/smp: Support more IPI messages
  powerpc/smp: Add smp_muxed_ipi_rm_message_pass

 arch/powerpc/include/asm/smp.h |  4 ++++
 arch/powerpc/kernel/smp.c      | 38 ++++++++++++++++++++++++++++++++++----
 2 files changed, 38 insertions(+), 4 deletions(-)

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1.8.3.4