Comment 3 for bug 1586756

Sorry, this issue only occur in qemu-system-arm (vexpress-a9).
In hw/char/pl011.c, qemu_chr_fe_write function is called directly and EAGAIN isn't handled.

http://git.qemu.org/?p=qemu.git;a=blob;f=hw/char/pl011.c;h=210c87b4c2bd000d80c359ca5c05d43c64210677;hb=bfc766d38e1fae5767d43845c15c79ac8fa6d6af#l148

So I use following a patch.

----
diff --git a/hw/char/pl011.c b/hw/char/pl011.c
index c0fbf8a..6e29db8 100644
--- a/hw/char/pl011.c
+++ b/hw/char/pl011.c
@@ -146,7 +146,7 @@ static void pl011_write(void *opaque, hwaddr offset,
         /* ??? Check if transmitter is enabled. */
         ch = value;
         if (s->chr)
- qemu_chr_fe_write(s->chr, &ch, 1);
+ qemu_chr_fe_write_all(s->chr, &ch, 1);
         s->int_level |= PL011_INT_TX;
         pl011_update(s);
         break;
----

qemu_chr_fe_write_all function handles EAGAIN.