mem-sharing: move (x86) / drop (Arm) arch_dump_shared_mem_info()

When !MEM_SHARING no useful output is produced. Move the function into
mm/mem_sharing.c while conditionalizing the call to it, thus allowing to
drop it altogether from Arm (and eliminating the need to introduce stubs
on PPC and RISC-V).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com> #arm
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>

xen/arch/arm/mm.c

@@ -1294,10 +1294,6 @@ void free_init_memory(void)
     printk("Freed %ldkB init memory.\n", (long)(__init_end-__init_begin)>>10);
 }
 
-void arch_dump_shared_mem_info(void)
-{
-}
-
 int steal_page(
     struct domain *d, struct page_info *page, unsigned int memflags)
 {

xen/arch/x86/mm.c

@@ -6261,13 +6261,6 @@ void memguard_unguard_stack(void *p)
     map_pages_to_xen((unsigned long)p, virt_to_mfn(p), 1, PAGE_HYPERVISOR_RW);
 }
 
-void arch_dump_shared_mem_info(void)
-{
-    printk("Shared frames %u -- Saved frames %u\n",
-            mem_sharing_get_nr_shared_mfns(),
-            mem_sharing_get_nr_saved_mfns());
-}
-
 const struct platform_bad_page *__init get_platform_badpages(unsigned int *array_size)
 {
     u32 igd_id;

xen/arch/x86/mm/mem_sharing.c

@@ -2329,3 +2329,10 @@ int mem_sharing_domctl(struct domain *d, struct xen_domctl_mem_sharing_op *mec)
 
     return rc;
 }
+
+void arch_dump_shared_mem_info(void)
+{
+    printk("Shared frames %u -- Saved frames %u\n",
+            mem_sharing_get_nr_shared_mfns(),
+            mem_sharing_get_nr_saved_mfns());
+}

xen/common/keyhandler.c

@@ -365,7 +365,9 @@ static void cf_check dump_domains(unsigned char key)
         }
     }
 
+#ifdef CONFIG_MEM_SHARING
     arch_dump_shared_mem_info();
+#endif
 
     rcu_read_unlock(&domlist_read_lock);
 }