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-rw-r--r--arch/x86/include/asm/xen/page.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 1a162e559753..7068e4bb057d 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -87,6 +87,18 @@ clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
#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 XEN_EXTRA_MEM_RATIO (10)
+
+/*
* Helper functions to write or read unsigned long values to/from
* memory, when the access may fault.
*/