x86/MTRR: fix range check in mtrr_add_page()

Extracted from Yinghai Lu's Linux commit d5c78673 ("x86: Fix /proc/mtrr
with base/size more than 44bits").

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/cpu/mtrr/main.c
+++ b/xen/arch/x86/cpu/mtrr/main.c
@@ -340,7 +340,7 @@ int mtrr_add_page(unsigned long base, un
 		return -EINVAL;
 	}
 
-	if (base & size_or_mask || size & size_or_mask) {
+	if ((base | (base + size - 1)) >> (paddr_bits - PAGE_SHIFT)) {
 		printk(KERN_WARNING "mtrr: base or size exceeds the MTRR width\n");
 		return -EINVAL;
 	}