KVM: Purify x86_decode_insn() error case management

The only valid case is on protected page access, other cases are errors.

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 2d55bab41634..888b0924c17b 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1251,7 +1251,7 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
                         u16 error_code,
                         int no_decode)
 {
-        int r = 0;
+        int r;
 
         vcpu->mmio_fault_cr2 = cr2;
         kvm_x86_ops->cache_regs(vcpu);
@@ -1294,10 +1294,14 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
                                         get_segment_base(vcpu, VCPU_SREG_FS);
 
                 r = x86_decode_insn(&vcpu->emulate_ctxt, &emulate_ops);
+                if (r)  {
+                        if (kvm_mmu_unprotect_page_virt(vcpu, cr2))
+                                return EMULATE_DONE;
+                        return EMULATE_FAIL;
+                }
         }
 
-        if (r == 0)
-                r = x86_emulate_insn(&vcpu->emulate_ctxt, &emulate_ops);
+        r = x86_emulate_insn(&vcpu->emulate_ctxt, &emulate_ops);
 
         if (vcpu->pio.string)
                 return EMULATE_DO_MMIO;