From ea460580ae8d4910bddac476b25eb31c04b4e54c Mon Sep 17 00:00:00 2001 From: David Gibson Date: Mon, 27 Nov 2017 04:56:27 +0100 Subject: [PATCH 5/7] spapr: Implement bug in spapr-vty device to be compatible with PowerVM RH-Author: David Gibson Message-id: <20171127045627.20341-1-dgibson@redhat.com> Patchwork-id: 77896 O-Subject: [RHEL-7.5 qemu-kvm-rhev PATCH] spapr: Implement bug in spapr-vty device to be compatible with PowerVM Bugzilla: 1495090 RH-Acked-by: Thomas Huth RH-Acked-by: Laurent Vivier RH-Acked-by: Miroslav Rezanina From: David Gibson 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 Reviewed-by: Thomas Huth Reviewed-by: Greg Kurz (cherry picked from commit 6c3bc244d3cbdc5545504fda4fae0238ec36a3c0) Testing: Verified that when transferring a file (raw) through spapr-vty device, '\r\0' sequences are no longer mangled. Signed-off-by: David Gibson Signed-off-by: Miroslav Rezanina --- hw/char/spapr_vty.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/hw/char/spapr_vty.c b/hw/char/spapr_vty.c index 0fa416c..6748334 100644 --- a/hw/char/spapr_vty.c +++ b/hw/char/spapr_vty.c @@ -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); -- 1.8.3.1