[PATCH] tty: hvc: don't allocate a buffer for console print on stack

[Jan Dakinevich]

The buffer is used by virtio console driver as DMA buffer. Since v4.9
(if VMAP_STACK is enabled) we shouldn't use the stack for DMA.

Signed-off-by: Jan Dakinevich <jan.dakinevich at gmail.com>
---
 drivers/tty/hvc/hvc_console.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 9b5c0fb..1ce6aaf 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -143,10 +143,15 @@ static struct hvc_struct *hvc_get_by_index(int index)
 static void hvc_console_print(struct console *co, const char *b,
 			      unsigned count)
 {
-	char c[N_OUTBUF] __ALIGNED__;
 	unsigned i = 0, n = 0;
 	int r, donecr = 0, index = co->index;
 
+	/*
+	 * Access to the buffer is serialized by console_sem in caller code from
+	 * kernel/printk/printk.c
+	 */
+	static char c[N_OUTBUF] __ALIGNED__;
+
 	/* Console access attempt outside of acceptable console range. */
 	if (index >= MAX_NR_HVC_CONSOLES)
 		return;
-- 
1.9.1