[IA64] pvops: preparation: introduce ia64_get_psr_i() to make kernel paravirtualization friendly.

__local_irq_save() and local_save_flags() are used to mask interruptions.
They read all psr bits that requres whole bit emulation.
On the other hand, reading only psr.i, the single bit, can be virtualized
cheaply.
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>

include/asm-ia64/intrinsics.h

@@ -18,6 +18,8 @@
 # include <asm/gcc_intrin.h>
 #endif
 
+#define ia64_get_psr_i()	(ia64_getreg(_IA64_REG_PSR) & IA64_PSR_I)
+
 #define ia64_set_rr0_to_rr4(val0, val1, val2, val3, val4)	\
 do {								\
 	ia64_set_rr(0x0000000000000000UL, (val0));		\

include/asm-ia64/system.h

@@ -123,10 +123,16 @@ extern struct ia64_boot_param {
  *   write a floating-point register right before reading the PSR
  *   and that writes to PSR.mfl
  */
+#ifdef CONFIG_PARAVIRT
+#define __local_save_flags()	ia64_get_psr_i()
+#else
+#define __local_save_flags()	ia64_getreg(_IA64_REG_PSR)
+#endif
+
 #define __local_irq_save(x)			\
 do {						\
 	ia64_stop();				\
-	(x) = ia64_getreg(_IA64_REG_PSR);	\
+	(x) = __local_save_flags();		\
 	ia64_stop();				\
 	ia64_rsm(IA64_PSR_I);			\
 } while (0)
@@ -174,7 +180,7 @@ do {								\
 #endif /* !CONFIG_IA64_DEBUG_IRQ */
 
 #define local_irq_enable()	({ ia64_stop(); ia64_ssm(IA64_PSR_I); ia64_srlz_d(); })
-#define local_save_flags(flags)	({ ia64_stop(); (flags) = ia64_getreg(_IA64_REG_PSR); })
+#define local_save_flags(flags)	({ ia64_stop(); (flags) = __local_save_flags(); })
 
 #define irqs_disabled()				\
 ({						\