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-rw-r--r--arch/x86/xen/xen-ops.h14
1 files changed, 14 insertions, 0 deletions
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index a87ab36889e76c..79cf93f2c92f1d 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -163,4 +163,18 @@ void xen_hvm_post_suspend(int suspend_cancelled);
static inline void xen_hvm_post_suspend(int suspend_cancelled) {}
#endif
+/*
+ * The maximum amount of extra memory compared to the base size. The
+ * main scaling factor is the size of struct page. At extreme ratios
+ * of base:extra, all the base memory can be filled with page
+ * structures for the extra memory, leaving no space for anything
+ * else.
+ *
+ * 10x seems like a reasonable balance between scaling flexibility and
+ * leaving a practically usable system.
+ */
+#define EXTRA_MEM_RATIO (10)
+
+void xen_add_extra_mem(unsigned long start_pfn, unsigned long n_pfns);
+
#endif /* XEN_OPS_H */