KVM: MIPS: Override HVA error values for EVA

MIPS Enhanced Virtual Addressing (EVA) allows the user mode and kernel
mode address spaces to overlap, breaking the assumption that PAGE_OFFSET
is an appropriate KVM HVA error value, since PAGE_OFFSET may be as low
as zero.

Fix this in the same way that s390 does in commit bf640876e21f ("KVM:
s390: Make KVM_HVA_ERR_BAD usable on s390"), by overriding
KVM_HVA_ERR_[RO_]BAD and kvm_is_error_hva() in asm/kvm_host.h.

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/include/asm/kvm_host.h

@@ -107,6 +107,20 @@
 #define KVM_INVALID_INST		0xdeadbeef
 #define KVM_INVALID_ADDR		0xdeadbeef
 
+/*
+ * EVA has overlapping user & kernel address spaces, so user VAs may be >
+ * PAGE_OFFSET. For this reason we can't use the default KVM_HVA_ERR_BAD of
+ * PAGE_OFFSET.
+ */
+
+#define KVM_HVA_ERR_BAD			(-1UL)
+#define KVM_HVA_ERR_RO_BAD		(-2UL)
+
+static inline bool kvm_is_error_hva(unsigned long addr)
+{
+	return IS_ERR_VALUE(addr);
+}
+
 extern atomic_t kvm_mips_instance;
 
 struct kvm_vm_stat {