[PATCH 1/3] x86/pv: Don't deliver #GP for a SYSENTER with NT set

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

It is a matter of guest kernel policy what to do with offending userspace, and
terminating said userspace may not be the action chosen.

Linux explicitly tolerates this case.

Reported-by: Andy Lutomirski <luto@xxxxxxxxxx>
Fixes: fdac951560 ("x86: clear EFLAGS.NT in SYSENTER entry path")
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Andy Lutomirski <luto@xxxxxxxxxx>
---
 xen/arch/x86/x86_64/entry.S | 1 -
 1 file changed, 1 deletion(-)

diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 71a00e846b..44a110b9c8 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -313,7 +313,6 @@ UNLIKELY_START(nz, sysenter_nt_set)
         pushfq
         andl  $~X86_EFLAGS_NT,(%rsp)
         popfq
-        xorl  %eax,%eax
 UNLIKELY_END(sysenter_nt_set)
         testq %rax,%rax
         leal  (,%rcx,TBF_INTERRUPT),%ecx
-- 
2.11.0