[PATCH 1/3] x86/irq: local_irq_restore() should not blindly popf

[Andrew Cooper <andrew.cooper3@citrix.com>]

local_irq_restore() should only be concerned with possibly changing the
interrupt flag.  A blind popf could corrupt other system flags.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <JBeulich@suse.com>
---
 xen/include/asm-x86/system.h |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/include/asm-x86/system.h b/xen/include/asm-x86/system.h
index 6ab7d56..cbf0f6a 100644
--- a/xen/include/asm-x86/system.h
+++ b/xen/include/asm-x86/system.h
@@ -159,8 +159,10 @@ static always_inline unsigned long __cmpxchg(
 #define local_irq_restore(x)                                     \
 ({                                                               \
     BUILD_BUG_ON(sizeof(x) != sizeof(long));                     \
-    asm volatile ( "push" __OS " %0 ; popf" __OS                 \
-                   : : "g" (x) : "memory", "cc" );               \
+    if ( x & X86_EFLAGS_IF )                                     \
+        local_irq_enable();                                      \
+    else                                                         \
+        local_irq_disable();                                     \
 })
 
 static inline int local_irq_is_enabled(void)
-- 
1.7.10.4