Commit 6c3bc244 authored Nov 20, 2017 by David Gibson

spapr: Implement bug in spapr-vty device to be compatible with PowerVM



The spapr-vty device implements the PAPR defined virtual console,
which is also implemented by IBM's proprietary PowerVM hypervisor.

PowerVM's implementation has a bug where it inserts an extra \0 after
every \r going to the guest.  Because of that Linux's guest side
driver has a workaround which strips \0 characters that appear
immediately after a \r.

That means that when running under qemu, sending a binary stream from
host to guest via spapr-vty which happens to include a \r\0 sequence
will get corrupted by that workaround.

To deal with that, this patch duplicates PowerVM's bug, inserting an
extra \0 after each \r.  Ugly, but the best option available.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>

parent bac658d1

hw/char/spapr_vty.c

+18 −0

Original line number	Diff line number	Diff line
		@@ -58,6 +58,24 @@ static int vty_getchars(VIOsPAPRDevice sdev, uint8_t buf, int max)

		while ((n < max) && (dev->out != dev->in)) {
		buf[n++] = dev->buf[dev->out++ % VTERM_BUFSIZE];

		/* PowerVM's vty implementation has a bug where it inserts a
		* \0 after every \r going to the guest. Existing guests have
		* a workaround for this which removes every \0 immediately
		* following a \r, so here we make ourselves bug-for-bug
		* compatible, so that the guest won't drop a real \0-after-\r
		* that happens to occur in a binary stream. */
		if (buf[n - 1] == '\r') {
		if (n < max) {
		buf[n++] = '\0';
		} else {
		/* No room for the extra \0, roll back and try again
		* next time */
		dev->out--;
		n--;
		break;
		}
		}
		}

		qemu_chr_fe_accept_input(&dev->chardev);