lguest: fix on Intel when KVM loaded (unhandled trap 13)

When KVM is loaded, and hence VT set up, the vmcall instruction in an
lguest guest causes a #GP, not #UD.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 9 deletions

diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index 1a83910f674f..eaf722fe309a 100644
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -358,6 +358,16 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
                         if (emulate_insn(cpu))
                                 return;
                 }
+                /* If KVM is active, the vmcall instruction triggers a
+                 * General Protection Fault.  Normally it triggers an
+                 * invalid opcode fault (6): */
+        case 6:
+                /* We need to check if ring == GUEST_PL and
+                 * faulting instruction == vmcall. */
+                if (is_hypercall(cpu)) {
+                        rewrite_hypercall(cpu);
+                        return;
+                }
                 break;
         case 14: /* We've intercepted a Page Fault. */
                 /* The Guest accessed a virtual address that wasn't mapped.
@@ -403,15 +413,6 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
                  * up the pointer now to indicate a hypercall is pending. */
                 cpu->hcall = (struct hcall_args *)cpu->regs;
                 return;
-        case 6:
-                /* kvm hypercalls trigger an invalid opcode fault (6).
-                 * We need to check if ring == GUEST_PL and
-                 * faulting instruction == vmcall. */
-                if (is_hypercall(cpu)) {
-                        rewrite_hypercall(cpu);
-                        return;
-                }
-                break;
         }
 
         /* We didn't handle the trap, so it needs to go to the Guest. */