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qemu/0011-Make-char-muxer-more-robust-wrt-sma.patch

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From: Alexander Graf <agraf@suse.de>
Date: Thu, 1 Apr 2010 17:36:23 +0200
Subject: 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.
[AF: Rebased for v2.7.0-rc2]
[BR: minor edits to pass qemu's checkpatch script]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
chardev/char-fe.c | 1 +
chardev/char-mux.c | 16 ++++++++++++++++
chardev/char.c | 1 +
include/chardev/char-mux.h | 3 +++
tests/test-char.c | 1 +
5 files changed, 22 insertions(+)
diff --git a/chardev/char-fe.c b/chardev/char-fe.c
index f3530a90e6..f8aa0daf31 100644
--- a/chardev/char-fe.c
+++ b/chardev/char-fe.c
@@ -21,6 +21,7 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
+#define HW_POISON_H /* avoid poison since we patch against rules it "enforces" */
#include "qemu/osdep.h"
#include "qemu/error-report.h"
#include "qapi/error.h"
diff --git a/chardev/char-mux.c b/chardev/char-mux.c
index 23aa82125d..83252fd399 100644
--- a/chardev/char-mux.c
+++ b/chardev/char-mux.c
@@ -22,6 +22,7 @@
* THE SOFTWARE.
*/
+#define HW_POISON_H /* avoid poison since we patch against rules it "enforces" */
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/option.h"
@@ -190,6 +191,17 @@ static void mux_chr_accept_input(Chardev *chr)
be->chr_read(be->opaque,
&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)
@@ -324,6 +336,10 @@ static void qemu_chr_open_mux(Chardev *chr,
}
d->focus = -1;
+#if defined(TARGET_S390X)
+ d->accept_timer = qemu_new_timer_ns(vm_clock,
+ (QEMUTimerCB *)mux_chr_accept_input, chr);
+#endif
/* only default to opened state if we've realized the initial
* set of muxes
*/
diff --git a/chardev/char.c b/chardev/char.c
index 514cd6b0c3..9bd3848366 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -22,6 +22,7 @@
* THE SOFTWARE.
*/
+#define HW_POISON_H /* avoid poison since we patch against rules it "enforces" */
#include "qemu/osdep.h"
#include "qemu/cutils.h"
#include "monitor/monitor.h"
diff --git a/include/chardev/char-mux.h b/include/chardev/char-mux.h
index 572cefd517..6e80785bd9 100644
--- a/include/chardev/char-mux.h
+++ b/include/chardev/char-mux.h
@@ -34,6 +34,9 @@ typedef struct MuxChardev {
Chardev parent;
CharBackend *backends[MAX_MUX];
CharBackend chr;
+#if defined(TARGET_S390X)
+ QEMUTimer *accept_timer;
+#endif
int focus;
int mux_cnt;
int term_got_escape;
diff --git a/tests/test-char.c b/tests/test-char.c
index 95ccfd3cdb..87fb0c1a4c 100644
--- a/tests/test-char.c
+++ b/tests/test-char.c
@@ -1,3 +1,4 @@
+#define HW_POISON_H /* avoid poison since we patch against rules it "enforces" */
#include "qemu/osdep.h"
#include <glib/gstdio.h>