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