[Xen-devel] [PATCH] small adjustment to asm constraints for c/s 19400

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

Properly indicate the variable that the asm writes to, and allow
compiler more freedom in selecting a suitable input operand for the ltr
instruction.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- 2009-03-27.orig/xen/arch/x86/traps.c        2009-03-24 09:04:02.000000000 
+0100
+++ 2009-03-27/xen/arch/x86/traps.c     2009-03-27 10:10:57.000000000 +0100
@@ -3048,8 +3048,8 @@ void load_TR(void)
 
     /* Switch to non-compat GDT (which has B bit clear) to execute LTR. */
     asm volatile (
-        "sgdt %1; lgdt %2; ltr %%ax; lgdt %1"
-        : : "a" (TSS_ENTRY << 3), "m" (old_gdt), "m" (tss_gdt) : "memory" );
+        "sgdt %0; lgdt %2; ltr %w1; lgdt %0"
+        : "=m" (old_gdt) : "rm" (TSS_ENTRY << 3), "m" (tss_gdt) : "memory" );
 }
 
 void __devinit percpu_traps_init(void)




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