From 019288bf137183bf3407c9824655b753bfafc99f Mon Sep 17 00:00:00 2001 From: Sergio Lopez Date: Tue, 5 Jun 2018 03:54:55 -0400 Subject: [PATCH] hw/char/serial: Only retry if qemu_chr_fe_write returns 0 Only retry on serial_xmit if qemu_chr_fe_write returns 0, as this is the only recoverable error. Retrying with any other scenario, in addition to being a waste of CPU cycles, can compromise the Guest stability if by the vCPU issuing the write and the main loop thread are, by chance or explicit pinning, running on the same pCPU. Previous discussion: https://lists.nongnu.org/archive/html/qemu-devel/2018-05/msg06998.html Signed-off-by: Sergio Lopez Message-Id: <1528185295-14199-1-git-send-email-slp@redhat.com> Signed-off-by: Paolo Bonzini --- hw/char/serial.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/char/serial.c b/hw/char/serial.c index 605b0d02f9..6de6c29779 100644 --- a/hw/char/serial.c +++ b/hw/char/serial.c @@ -260,7 +260,7 @@ static void serial_xmit(SerialState *s) if (s->mcr & UART_MCR_LOOP) { /* in loopback mode, say that we just received a char */ serial_receive1(s, &s->tsr, 1); - } else if (qemu_chr_fe_write(&s->chr, &s->tsr, 1) != 1 && + } else if (qemu_chr_fe_write(&s->chr, &s->tsr, 1) == 0 && s->tsr_retry < MAX_XMIT_RETRY) { assert(s->watch_tag == 0); s->watch_tag =