Based on upstream commit:
d63bae0 KVM: X86: Add kvm hypervisor init time platform setup callback
aaffcfd KVM: X86: Implement PV IPIs in linux guest
Implement paravirtual apic hooks to enable PV IPIs for KVM if the "send IPI"
hypercall is available. The hypercall lets a guest send IPIs, with
at most 128 destinations per hypercall in 64-bit mode and 64 vCPUs per
hypercall in 32-bit mode.
Signed-off-by: loobinliu <loobinliu@tencent.com>