Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/include/xen/xen.h b/include/xen/xen.h
index 1e1d9bd..19a72f5 100644
--- a/include/xen/xen.h
+++ b/include/xen/xen.h
@@ -29,6 +29,9 @@
 
 extern uint32_t xen_start_flags;
 
+#include <xen/interface/hvm/start_info.h>
+extern struct hvm_start_info pvh_start_info;
+
 #ifdef CONFIG_XEN_DOM0
 #include <xen/interface/xen.h>
 #include <asm/xen/hypervisor.h>
@@ -39,4 +42,14 @@
 #define xen_initial_domain()	(0)
 #endif	/* CONFIG_XEN_DOM0 */
 
+struct bio_vec;
+struct page;
+
+bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
+		const struct page *page);
+
+#if defined(CONFIG_MEMORY_HOTPLUG) && defined(CONFIG_XEN_BALLOON)
+extern u64 xen_saved_max_mem_size;
+#endif
+
 #endif	/* _XEN_XEN_H */