From: Jan Beulich <jbeulich@suse.com>
Date: Wed, 23 Nov 2016 14:27:47 +0000 (+0100)
Subject: x86emul: in_longmode() should not ignore ->read_msr() errors
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~73
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=122dd9575c7a3b503e8f4aec64d16e8986a0bb91;p=xen.git

x86emul: in_longmode() should not ignore ->read_msr() errors

All present hook implementations succeed for EFER, but we shouldn't
really build on this being the case.

Suggested-by: George Dunlap <george.dunlap@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>
---

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index a85f45e2bb..04f0dac572 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -1296,10 +1296,10 @@ in_longmode(
 {
     uint64_t efer;
 
-    if (ops->read_msr == NULL)
+    if ( !ops->read_msr ||
+         unlikely(ops->read_msr(MSR_EFER, &efer, ctxt) != X86EMUL_OKAY) )
         return -1;
 
-    ops->read_msr(MSR_EFER, &efer, ctxt);
     return !!(efer & EFER_LMA);
 }