KVM: x86 emulator: Let compiler know insn_fetch() rarely fails

Fetching the instruction which was to be executed by the guest cannot
fail normally.  So compiler should always predict that it will succeed.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index d4cc8af67d95019d04d822d4df4d53f9a615091a..191bc9be49461789ceafd99fcf3c32f01103f609 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -672,11 +672,11 @@ static int do_insn_fetch_byte(struct x86_emulate_ctxt *ctxt, u8 *dest)
                size = min(15UL - cur_size,
                           PAGE_SIZE - offset_in_page(ctxt->_eip));
                rc = __linearize(ctxt, addr, size, false, true, &linear);
-               if (rc != X86EMUL_CONTINUE)
+               if (unlikely(rc != X86EMUL_CONTINUE))
                        return rc;
                rc = ctxt->ops->fetch(ctxt, linear, fc->data + cur_size,
                                      size, &ctxt->exception);
-               if (rc != X86EMUL_CONTINUE)
+               if (unlikely(rc != X86EMUL_CONTINUE))
                        return rc;
                fc->end += size;
        }
@@ -691,7 +691,7 @@ static int do_insn_fetch(struct x86_emulate_ctxt *ctxt,
        int rc;
 
        /* x86 instructions are limited to 15 bytes. */
-       if (ctxt->_eip + size - ctxt->eip > 15)
+       if (unlikely(ctxt->_eip + size - ctxt->eip > 15))
                return X86EMUL_UNHANDLEABLE;
        while (size--) {
                rc = do_insn_fetch_byte(ctxt, dest++);