[Qemu-devel] [PATCH RFC] ps2: set the keybord output buffer size as the same as kernel

[arei.gonglei]

From: Gonglei <address@hidden>

According to the PS/2 Mouse/Keyboard Protocol, the keyboard outupt buffer size
is 16 bytes. And the PS2_QUEUE_SIZE 256 was introduced in Qemu from the very
beginning.

When I started a  redhat5.6 32bit guest, meanwhile tapped the keyboard as 
quickly as
possible, the screen would show me "i8042.c: No controller found". As a result,
I couldn't use the keyboard in the VNC client.

Previous discussion about the issue in maillist:
http://thread.gmane.org/gmane.comp.emulators.qemu/43294/focus=47180

This patch has been tested on redhat5.6 32-bit/suse11sp3 64-bit guests.
More easy meathod to reproduce:
1.boot a guest with libvirt.
2.connect to VNC client.
3.as you see the BIOS, bootloader, Linux booting, run the follow simply shell 
script:
for((i=0;i<10000000;i++)) do virsh send-key redhat5.6 KEY_A; done

Actual results:
dmesg show "i8042.c: No controller found." And the keyboard is out of work.

Signed-off-by: Gonglei <address@hidden>
---
 hw/input/ps2.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/hw/input/ps2.c b/hw/input/ps2.c
index 3412079..a754fef 100644
--- a/hw/input/ps2.c
+++ b/hw/input/ps2.c
@@ -71,7 +71,7 @@
 #define MOUSE_STATUS_ENABLED    0x20
 #define MOUSE_STATUS_SCALE21    0x10
 
-#define PS2_QUEUE_SIZE 256
+#define PS2_QUEUE_SIZE 16     /* Keyboard output buffer size */
 
 typedef struct {
     uint8_t data[PS2_QUEUE_SIZE];
@@ -137,7 +137,7 @@ void ps2_queue(void *opaque, int b)
     PS2State *s = (PS2State *)opaque;
     PS2Queue *q = &s->queue;
 
-    if (q->count >= PS2_QUEUE_SIZE)
+    if (q->count >= PS2_QUEUE_SIZE - 1)
         return;
     q->data[q->wptr] = b;
     if (++q->wptr == PS2_QUEUE_SIZE)
@@ -375,7 +375,7 @@ static void ps2_mouse_event(void *opaque,
     }
 
     if (!(s->mouse_status & MOUSE_STATUS_REMOTE) &&
-        (s->common.queue.count < (PS2_QUEUE_SIZE - 16))) {
+        (s->common.queue.count < PS2_QUEUE_SIZE)) {
         for(;;) {
             /* if not remote, send event. Multiple events are sent if
                too big deltas */
-- 
1.6.0.2