From ba96da130a625a71b574c1bb9f6027e3b8d655ab Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 9 Jun 2017 11:43:59 +0200 Subject: [PATCH 4/6] serial: reinstate watch after migration RH-Author: Paolo Bonzini Message-id: <20170609114359.13036-4-pbonzini@redhat.com> Patchwork-id: 75566 O-Subject: [RHEL7.4 qemu-kvm PATCH v2 3/3] serial: reinstate watch after migration Bugzilla: 1452067 RH-Acked-by: David Hildenbrand RH-Acked-by: Dr. David Alan Gilbert RH-Acked-by: Laszlo Ersek Otherwise, a serial port can get stuck if it is migrated while flow control is in effect. Tested-by: Bret Ketchum Reviewed-by: Dr. David Alan Gilbert Signed-off-by: Paolo Bonzini (cherry picked from commit 9f34a35e0020b0b2b2e21c086a486d7dfd18df4f) Signed-off-by: Miroslav Rezanina --- hw/char/serial.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/hw/char/serial.c b/hw/char/serial.c index 0518a6f..820960b 100644 --- a/hw/char/serial.c +++ b/hw/char/serial.c @@ -637,13 +637,34 @@ static int serial_post_load(void *opaque, int version_id) if (version_id < 3) { s->fcr_vmstate = 0; } - if (s->tsr_retry > MAX_XMIT_RETRY) { - s->tsr_retry = MAX_XMIT_RETRY; - } - if (s->thr_ipending == -1) { s->thr_ipending = ((s->iir & UART_IIR_ID) == UART_IIR_THRI); } + + if (s->tsr_retry > 0) { + /* tsr_retry > 0 implies LSR.TEMT = 0 (transmitter not empty). */ + if (s->lsr & UART_LSR_TEMT) { + error_report("inconsistent state in serial device " + "(tsr empty, tsr_retry=%d", s->tsr_retry); + return -1; + } + + if (s->tsr_retry > MAX_XMIT_RETRY) { + s->tsr_retry = MAX_XMIT_RETRY; + } + + assert(s->watch_tag == 0); + s->watch_tag = qemu_chr_fe_add_watch(s->chr, G_IO_OUT|G_IO_HUP, + serial_watch_cb, s); + } else { + /* tsr_retry == 0 implies LSR.TEMT = 1 (transmitter empty). */ + if (!(s->lsr & UART_LSR_TEMT)) { + error_report("inconsistent state in serial device " + "(tsr not empty, tsr_retry=0"); + return -1; + } + } + s->last_break_enable = (s->lcr >> 6) & 1; /* Initialize fcr via setter to perform essential side-effects */ serial_write_fcr(s, s->fcr_vmstate); -- 1.8.3.1