SHA256
1
0
forked from pool/qemu
qemu/0032-Make-char-muxer-more-robust-wrt-sma.patch

65 lines
2.4 KiB
Diff

From ae8f274f387c2401d6e17cd9e9889aa0d76b1b9b Mon Sep 17 00:00:00 2001
From: Alexander Graf <agraf@suse.de>
Date: Thu, 1 Apr 2010 17:36:23 +0200
Subject: [PATCH] Make char muxer more robust wrt small FIFOs
Virtio-Console can only process one character at a time. Using it on S390
gave me strage "lags" where I got the character I pressed before when
pressing one. So I typed in "abc" and only received "a", then pressed "d"
but the guest received "b" and so on.
While the stdio driver calls a poll function that just processes on its
queue in case virtio-console can't take multiple characters at once, the
muxer does not have such callbacks, so it can't empty its queue.
To work around that limitation, I introduced a new timer that only gets
active when the guest can not receive any more characters. In that case
it polls again after a while to check if the guest is now receiving input.
This patch fixes input when using -nographic on s390 for me.
---
qemu-char.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/qemu-char.c b/qemu-char.c
index a405d76..471ccfe 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -403,6 +403,9 @@ typedef struct {
IOEventHandler *chr_event[MAX_MUX];
void *ext_opaque[MAX_MUX];
CharDriverState *drv;
+#if defined(TARGET_S390X)
+ QEMUTimer *accept_timer;
+#endif
int focus;
int mux_cnt;
int term_got_escape;
@@ -562,6 +565,15 @@ static void mux_chr_accept_input(CharDriverState *chr)
d->chr_read[m](d->ext_opaque[m],
&d->buffer[m][d->cons[m]++ & MUX_BUFFER_MASK], 1);
}
+
+#if defined(TARGET_S390X)
+ /* We're still not able to sync producer and consumer, so let's wait a bit
+ and try again by then. */
+ if (d->prod[m] != d->cons[m]) {
+ qemu_mod_timer(d->accept_timer, qemu_get_clock_ns(vm_clock)
+ + (int64_t)100000);
+ }
+#endif
}
static int mux_chr_can_read(void *opaque)
@@ -690,6 +702,10 @@ static CharDriverState *qemu_chr_open_mux(CharDriverState *drv)
chr->opaque = d;
d->drv = drv;
d->focus = -1;
+#if defined(TARGET_S390X)
+ d->accept_timer = qemu_new_timer_ns(vm_clock,
+ (QEMUTimerCB*)mux_chr_accept_input, chr);
+#endif
chr->chr_write = mux_chr_write;
chr->chr_update_read_handler = mux_chr_update_read_handler;
chr->chr_accept_input = mux_chr_accept_input;