KVM: MIPS/T&E: Ignore user writes to CP0_Config7

Ignore userland writes to CP0_Config7 rather than reporting an error,
since we do allow reads of this register and it is claimed to exist in
the ioctl API.

This allows userland to blindly save and restore KVM registers without
having to special case certain registers as not being writable, for
example during live migration once dirty page logging is fixed.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org

arch/mips/kvm/trap_emul.c

@@ -705,6 +705,9 @@ static int kvm_trap_emul_set_one_reg(struct kvm_vcpu *vcpu,
 			kvm_write_c0_guest_config5(cop0, v);
 		}
 		break;
+	case KVM_REG_MIPS_CP0_CONFIG7:
+		/* writes ignored */
+		break;
 	case KVM_REG_MIPS_COUNT_CTL:
 		ret = kvm_mips_set_count_ctl(vcpu, v);
 		break;