MIPS: KVM: Add vcpu_get_regs/vcpu_set_regs callback

Add a vcpu_get_regs() and vcpu_set_regs() callbacks for loading and
restoring context which may be in hardware registers. This may include
floating point and MIPS SIMD Architecture (MSA) state which may be
accessed directly by the guest (but restored lazily by the hypervisor),
and also dedicated guest registers as provided by the VZ ASE.

Signed-off-by: James Hogan <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Cc: Gleb Natapov <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]

arch/mips/include/asm/kvm_host.h

···
 			   const struct kvm_one_reg *reg, s64 *v);
 	int (*set_one_reg)(struct kvm_vcpu *vcpu,
 			   const struct kvm_one_reg *reg, s64 v);
+	int (*vcpu_get_regs)(struct kvm_vcpu *vcpu);
+	int (*vcpu_set_regs)(struct kvm_vcpu *vcpu);
 };
 extern struct kvm_mips_callbacks *kvm_mips_callbacks;
 int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks);

arch/mips/kvm/tlb.c

···
 		}
 	}
 
+	/* restore guest state to registers */
+	kvm_mips_callbacks->vcpu_set_regs(vcpu);
+
 	local_irq_restore(flags);
 
 }
···
 
 	vcpu->arch.preempt_entryhi = read_c0_entryhi();
 	vcpu->arch.last_sched_cpu = cpu;
+
+	/* save guest state in registers */
+	kvm_mips_callbacks->vcpu_get_regs(vcpu);
 
 	if (((cpu_context(cpu, current->mm) ^ asid_cache(cpu)) &
 	     ASID_VERSION_MASK)) {

arch/mips/kvm/trap_emul.c

···
 	return ret;
 }
 
+static int kvm_trap_emul_vcpu_get_regs(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+
+static int kvm_trap_emul_vcpu_set_regs(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+
 static struct kvm_mips_callbacks kvm_trap_emul_callbacks = {
 	/* exit handlers */
 	.handle_cop_unusable = kvm_trap_emul_handle_cop_unusable,
···
 	.irq_clear = kvm_mips_irq_clear_cb,
 	.get_one_reg = kvm_trap_emul_get_one_reg,
 	.set_one_reg = kvm_trap_emul_set_one_reg,
+	.vcpu_get_regs = kvm_trap_emul_vcpu_get_regs,
+	.vcpu_set_regs = kvm_trap_emul_vcpu_set_regs,
 };
 
 int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks)