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, 6 insertions, 1 deletions

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 07ce10e3627a..29afd96069ef 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -1343,6 +1343,7 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
         u32 __user *opc = (u32 __user *) vcpu->arch.pc;
         unsigned long badvaddr = vcpu->arch.host_cp0_badvaddr;
         enum emulation_result er = EMULATE_DONE;
+        u32 inst;
         int ret = RESUME_GUEST;
 
         /* re-enable HTW before enabling interrupts */
@@ -1467,8 +1468,12 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
                 break;
 
         default:
+                if (cause & CAUSEF_BD)
+                        opc += 1;
+                inst = 0;
+                kvm_get_inst(opc, vcpu, &inst);
                 kvm_err("Exception Code: %d, not yet handled, @ PC: %p, inst: 0x%08x  BadVaddr: %#lx Status: %#lx\n",
-                        exccode, opc, kvm_get_inst(opc, vcpu), badvaddr,
+                        exccode, opc, inst, badvaddr,
                         kvm_read_c0_guest_status(vcpu->arch.cop0));
                 kvm_arch_vcpu_dump_regs(vcpu);
                 run->exit_reason = KVM_EXIT_INTERNAL_ERROR;