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-rw-r--r--arch/x86/xen/setup.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 1a3b75652fa4..8bfc10330107 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -59,6 +59,18 @@ static struct {
} xen_remap_buf __initdata __aligned(PAGE_SIZE);
static unsigned long xen_remap_mfn __initdata = INVALID_P2M_ENTRY;
+/*
+ * 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)
+
static bool xen_512gb_limit __initdata = IS_ENABLED(CONFIG_XEN_512GB);
static void __init xen_parse_512gb(void)
@@ -778,13 +790,13 @@ char * __init xen_memory_setup(void)
extra_pages += max_pages - max_pfn;
/*
- * Clamp the amount of extra memory to a XEN_EXTRA_MEM_RATIO
+ * Clamp the amount of extra memory to a EXTRA_MEM_RATIO
* factor the base size.
*
* Make sure we have no memory above max_pages, as this area
* isn't handled by the p2m management.
*/
- extra_pages = min3(XEN_EXTRA_MEM_RATIO * min(max_pfn, PFN_DOWN(MAXMEM)),
+ extra_pages = min3(EXTRA_MEM_RATIO * min(max_pfn, PFN_DOWN(MAXMEM)),
extra_pages, max_pages - max_pfn);
i = 0;
addr = xen_e820_table.entries[0].addr;