Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/tools/virtio/linux/dma-mapping.h b/tools/virtio/linux/dma-mapping.h
index f91aeb5..8f41cd6 100644
--- a/tools/virtio/linux/dma-mapping.h
+++ b/tools/virtio/linux/dma-mapping.h
@@ -29,4 +29,6 @@
 #define dma_unmap_single(...) do { } while (0)
 #define dma_unmap_page(...) do { } while (0)
 
+#define dma_max_mapping_size(...) SIZE_MAX
+
 #endif
diff --git a/tools/virtio/linux/kernel.h b/tools/virtio/linux/kernel.h
index fb22bcc..6683b4a 100644
--- a/tools/virtio/linux/kernel.h
+++ b/tools/virtio/linux/kernel.h
@@ -23,6 +23,10 @@
 #define PAGE_MASK (~(PAGE_SIZE-1))
 #define PAGE_ALIGN(x) ((x + PAGE_SIZE - 1) & PAGE_MASK)
 
+/* generic data direction definitions */
+#define READ                    0
+#define WRITE                   1
+
 typedef unsigned long long phys_addr_t;
 typedef unsigned long long dma_addr_t;
 typedef size_t __kernel_size_t;
@@ -123,7 +127,7 @@
 #define dev_err(dev, format, ...) fprintf (stderr, format, ## __VA_ARGS__)
 #define dev_warn(dev, format, ...) fprintf (stderr, format, ## __VA_ARGS__)
 
-#define WARN_ON_ONCE(cond) ((cond) ? fprintf (stderr, "WARNING\n") : 0)
+#define WARN_ON_ONCE(cond) (unlikely(cond) ? fprintf (stderr, "WARNING\n") : 0)
 
 #define min(x, y) ({				\
 	typeof(x) _min1 = (x);			\