KVM: MIPS: Improve kvm_get_inst() error return

Currently kvm_get_inst() returns KVM_INVALID_INST in the event of a
fault reading the guest instruction. This has the rather arbitrary magic
value 0xdeadbeef. This API isn't very robust, and in fact 0xdeadbeef is
a valid MIPS64 instruction encoding, namely "ld t1,-16657(s5)".

Therefore change the kvm_get_inst() API to return 0 or -EFAULT, and to
return the instruction via a u32 *out argument. We can then drop the
KVM_INVALID_INST definition entirely.

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

1 files changed, 4 insertions, 5 deletions

diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c
index aab604e75d3b..6379ac1bc7b9 100644
--- a/arch/mips/kvm/mmu.c
+++ b/arch/mips/kvm/mmu.c
@@ -503,16 +503,15 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 	local_irq_restore(flags);
 }
 
-u32 kvm_get_inst(u32 *opc, struct kvm_vcpu *vcpu)
+int kvm_get_inst(u32 *opc, struct kvm_vcpu *vcpu, u32 *out)
 {
-	u32 inst;
 	int err;
 
-	err = get_user(inst, opc);
+	err = get_user(*out, opc);
 	if (unlikely(err)) {
 		kvm_err("%s: illegal address: %p\n", __func__, opc);
-		return KVM_INVALID_INST;
+		return -EFAULT;
 	}
 
-	return inst;
+	return 0;
 }