arm/arm64: KVM: Statically configure the host's view of MPIDR

We currently eagerly save/restore MPIDR. It turns out to be
slightly pointless:
- On the host, this value is known as soon as we're scheduled on a
  physical CPU
- In the guest, this value cannot change, as it is set by KVM
  (and this is a read-only register)

The result of the above is that we can perfectly avoid the eager
saving of MPIDR_EL1, and only keep the restore. We just have
to setup the host contexts appropriately at boot time.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>

arch/arm64/include/asm/kvm_host.h

@@ -30,6 +30,7 @@
 #include <asm/kvm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmio.h>
+#include <asm/smp_plat.h>
 #include <asm/thread_info.h>
 
 #define __KVM_HAVE_ARCH_INTC_INITIALIZED
@@ -418,6 +419,13 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
 
 DECLARE_PER_CPU(kvm_cpu_context_t, kvm_host_cpu_state);
 
+static inline void kvm_init_host_cpu_context(kvm_cpu_context_t *cpu_ctxt,
+					     int cpu)
+{
+	/* The host's MPIDR is immutable, so let's set it up at boot time */
+	cpu_ctxt->sys_regs[MPIDR_EL1] = cpu_logical_map(cpu);
+}
+
 void __kvm_enable_ssbs(void);
 
 static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,