powerpc/44x: declare tlb_44x_index for use in C code

KVM currently ignores the host's round robin TLB eviction selection, instead
maintaining its own TLB state and its own round robin index. However, by
participating in the normal 44x TLB selection, we can drop the alternate TLB
processing in KVM. This results in a significant performance improvement,
since that processing currently must be done on *every* guest exit.

Accordingly, KVM needs to be able to access and increment tlb_44x_index.
(KVM on 440 cannot be a module, so there is no need to export this symbol.)

Signed-off-by: Hollis Blanchard <[email protected]>
Acked-by: Josh Boyer <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>

arch/powerpc/include/asm/mmu-44x.h

@@ -56,6 +56,7 @@
 #ifndef __ASSEMBLY__
 
 extern unsigned int tlb_44x_hwater;
+extern unsigned int tlb_44x_index;
 
 typedef struct {
 	unsigned int	id;