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From ea460580ae8d4910bddac476b25eb31c04b4e54c Mon Sep 17 00:00:00 2001
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From: David Gibson <dgibson@redhat.com>
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Date: Mon, 27 Nov 2017 04:56:27 +0100
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Subject: [PATCH 5/7] spapr: Implement bug in spapr-vty device to be compatible
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with PowerVM
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RH-Author: David Gibson <dgibson@redhat.com>
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Message-id: <20171127045627.20341-1-dgibson@redhat.com>
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Patchwork-id: 77896
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O-Subject: [RHEL-7.5 qemu-kvm-rhev PATCH] spapr: Implement bug in spapr-vty device to be compatible with PowerVM
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Bugzilla: 1495090
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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From: David Gibson <david@gibson.dropbear.id.au>
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The spapr-vty device implements the PAPR defined virtual console,
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which is also implemented by IBM's proprietary PowerVM hypervisor.
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PowerVM's implementation has a bug where it inserts an extra \0 after
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every \r going to the guest. Because of that Linux's guest side
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driver has a workaround which strips \0 characters that appear
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immediately after a \r.
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That means that when running under qemu, sending a binary stream from
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host to guest via spapr-vty which happens to include a \r\0 sequence
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will get corrupted by that workaround.
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To deal with that, this patch duplicates PowerVM's bug, inserting an
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extra \0 after each \r. Ugly, but the best option available.
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Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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Reviewed-by: Thomas Huth <thuth@redhat.com>
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Reviewed-by: Greg Kurz <groug@kaod.org>
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(cherry picked from commit 6c3bc244d3cbdc5545504fda4fae0238ec36a3c0)
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Testing: Verified that when transferring a file (raw) through
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spapr-vty device, '\r\0' sequences are no longer mangled.
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Signed-off-by: David Gibson <dgibson@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/char/spapr_vty.c | 18 ++++++++++++++++++
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1 file changed, 18 insertions(+)
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diff --git a/hw/char/spapr_vty.c b/hw/char/spapr_vty.c
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index 0fa416c..6748334 100644
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--- a/hw/char/spapr_vty.c
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+++ b/hw/char/spapr_vty.c
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@@ -58,6 +58,24 @@ static int vty_getchars(VIOsPAPRDevice *sdev, uint8_t *buf, int max)
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while ((n < max) && (dev->out != dev->in)) {
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buf[n++] = dev->buf[dev->out++ % VTERM_BUFSIZE];
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+
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+ /* PowerVM's vty implementation has a bug where it inserts a
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+ * \0 after every \r going to the guest. Existing guests have
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+ * a workaround for this which removes every \0 immediately
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+ * following a \r, so here we make ourselves bug-for-bug
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+ * compatible, so that the guest won't drop a real \0-after-\r
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+ * that happens to occur in a binary stream. */
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+ if (buf[n - 1] == '\r') {
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+ if (n < max) {
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+ buf[n++] = '\0';
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+ } else {
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+ /* No room for the extra \0, roll back and try again
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+ * next time */
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+ dev->out--;
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+ n--;
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+ break;
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+ }
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+ }
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}
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qemu_chr_fe_accept_input(&dev->chardev);
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--
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1.8.3.1
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