powerpc: Make vmalloc_to_phys() public

This makes vmalloc_to_phys() public as there will be another user
(KVM in-kernel VFIO acceleration) for it soon. As this new user
can be compiled as a module, this exports the symbol.

As a little optimization, this changes the helper to call
vmalloc_to_pfn() instead of vmalloc_to_page() as the size of the
struct page may not be power-of-two aligned which will make gcc use
multiply instructions instead of shifts.

Signed-off-by: Alexey Kardashevskiy <[e-mail]>
Acked-by: Michael Ellerman <[e-mail]>
Reviewed-by: David Gibson <[e-mail]>
Signed-off-by: Paul Mackerras <[e-mail]>

arch/powerpc/include/asm/pgtable.h

···
 	}
 	return __find_linux_pte_or_hugepte(pgdir, ea, is_thp, shift);
 }
+
+unsigned long vmalloc_to_phys(void *vmalloc_addr);
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_PGTABLE_H */

arch/powerpc/mm/pgtable.c

···
 }
 #endif /* CONFIG_DEBUG_VM */
 
+unsigned long vmalloc_to_phys(void *va)
+{
+	unsigned long pfn = vmalloc_to_pfn(va);
+
+	BUG_ON(!pfn);
+	return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va);
+}
+EXPORT_SYMBOL_GPL(vmalloc_to_phys);

arch/powerpc/perf/hv-24x7.c

···
 	}
 }
 
-static unsigned long vmalloc_to_phys(void *v)
-{
-	struct page *p = vmalloc_to_page(v);
-
-	BUG_ON(!p);
-	return page_to_phys(p) + offset_in_page(v);
-}
-
 /* */
 struct event_uniq {
 	struct rb_node node;