[Qemu-devel] Re: [SOLUTION] "i8042.c: No controller found" ->OS sees no keyboard if I type "in BIOS"

["Dinesh Subhraveti" <subhraveti@gmail.com>]

"Dinesh Subhraveti" <dineshs@us.ibm.com> wrote in message 
news:loom.20090709T005828-509@post.gmane.org...
> Marcelo Tosatti <mtosatti <at> redhat.com> writes:
>
>>
>> On Wed, May 20, 2009 at 03:30:09PM +0200, Tomasz Chmielewski wrote:
>> > Tomasz Chmielewski schrieb:
>> >
>> >>> When I boot the guest and type (just hit any keys) in the VNC window
>> >>> before the operating system boots, sometimes, the system loads with
>> >>> no keyboard present - as signified in dmesg on guest:
>> >>>
>> >>> i8042.c: No controller found
>> >>>
>> >>> As a result, I can't use the keyboard in the VNC window.
>> >
>> >> drivers/input/serio/i8042.c in the Linux kerne has this:
>> >>
>> >> static int i8042_controller_check(void)
>> >> {
>> >>         if (i8042_flush() == I8042_BUFFER_SIZE) {
>> >>                 printk(KERN_ERR "i8042.c: No controller found.\n");
>> >>                 return -ENODEV;
>> >>         }
>> >>
>> >>         return 0;
>> >> }
>> >>
>> >>
>> >> So, can it be that if we type anything on keyboard (or move mouse)
>> >> while Qemu's BIOS is still booting or later in the bootloader (GRUB,
>> >> lilo), some buffer is not flushed and Linux gets confused? And as a
>> >> result, decides there is no keyboard?
>> >
>> > Yes, this is what seems to happen - Qemu's keyboard buffer seems to be
> infinite
>> > or at least very big; normal 8042 devices have buffer of 16 bytes only.
>> >
>> > If we add "i8042.debug" parameter to kernel command line,
>> > we will see how many characters were flushed during boot, i.e.:
>> >
>> >
>> > drivers/input/serio/i8042.c: ff <- i8042 (flush, aux) [0]
>> > drivers/input/serio/i8042.c: 18 <- i8042 (flush, aux) [0]
>> > drivers/input/serio/i8042.c: 92 <- i8042 (flush, aux) [0]
>> > drivers/input/serio/i8042.c: 00 <- i8042 (flush, aux) [0]
>> > (...)
>> >
>> >
>> > With this 16 byte buffer in drivers/input/serio/i8042.h (before 2.6.11 
>> > it
> was
>> > 32 bytes I think):
>> >
>> > #define I8042_BUFFER_SIZE       16
>> >
>> >
>> > and this piece of code in drivers/input/serio/i8042.c:
>> >
>> >
>> > /*
>> > * i8042_flush() flushes all data that may be in the keyboard and mouse
> buffers
>> > * of the i8042 down the toilet.
>> > */
>> >
>> > static int i8042_flush(void)
>> > {
>> >        unsigned long flags;
>> >        unsigned char data, str;
>> >        int i = 0;
>> >
>> >        spin_lock_irqsave(&i8042_lock, flags);
>> >
>> >        while (((str = i8042_read_status()) & I8042_STR_OBF) && (i <
> I8042_BUFFER_SIZE)) {
>> >                udelay(50);
>> >                data = i8042_read_data();
>> >                i++;
>> >                dbg("%02x <- i8042 (flush, %s)", data,
>> >                        str & I8042_STR_AUXDATA ? "aux" : "kbd");
>> >        }
>> >
>> >        spin_unlock_irqrestore(&i8042_lock, flags);
>> >
>> >        return i;
>> > }
>> >
>> >
>> >
>> > Linux kernel thinks there is no controller:
>> >
>> >
>> > (...)
>> > drivers/input/serio/i8042.c: 28 <- i8042 (flush, aux) [0]
>> > drivers/input/serio/i8042.c: 00 <- i8042 (flush, aux) [0]
>> > i8042.c: No controller found.
>> >
>> >
>> > If we increase "I8042_BUFFER_SIZE" to 256 or more, we have a much 
>> > better
>> > chance that a booted Linux will have a keyboard present.
>> >
>> > So, who's to be blamed?
>> >
>> > Linux kernel for having its i8042 buffer to small (16 bytes), fixable 
>> > with:
>> >
>> >
>> > --- i8042.h.orig        2009-05-20 15:26:32.000000000 +0200
>> > +++ i8042.h     2009-05-20 15:26:32.000000000 +0200
>> > @@ -73,7 +73,7 @@
>> >  * the i8042 buffers.
>> >  */
>> >
>> > -#define I8042_BUFFER_SIZE      16
>> > +#define I8042_BUFFER_SIZE      256
>> >
>> > /*
>> >  * Number of AUX ports on controllers supporting active multiplexing
>> >
>> >
>> >
>> > Or Qemu, for having its keyboard buffer too large (I'm not sure, but
> probably 256 bytes)?
>>
>> All references (*) i could find mention 16 bytes of output buffer
>> (including the Linux source as you mentioned, which was reduced from 32
>> to 16 somewhere in the 2.6.10 era).
>>
>> http://www.computer-engineering.org/ps2protocol/
>>
>> http://linux.bkbits.net:8080/linux-2.6.28-stable/drivers/input/serio/i8042.h?
> PAGE=diffs&REV=4203735dp_doSExYU6ido8KnczbjzQ
>>
>> Reducing PS2_QUEUE_SIZE to 16 also makes the Linux detection loop happy.
>>
>> If QEMU claims to emulate i8042, it should be similar to real hardware.
>
> Some new findings on this old thread:
>
> Reducing PS2_QUEUE_SIZE to 16 prevents the PS2 mouse event handler
> (ps2_mouse_event()) from queuing any mouse events.  It checks if there is 
> at
> least 16 bytes of space left in the queue, if not, the event is dropped.
>
> The side effect of this is that, the buffer will not become full, and
> i8042_controller_check() in the guest passes the check and keyboard works
> normally after reboot.  However, mouse remains inactive throughout, 
> because
> its events are always dropped.
>
> Two questions:
>
> - Does it make sense to reduce the size of reserved space (currently 16 
> bytes)
> checked by ps2_mouse_event()?  It will probably break other things since 
> the
> size of reserved space is tied to the distance mouse is moved.  If the
> distance moved can fit in 1 byte (+/- 128), it is queued as one event. 
> For
> longer distances, it is queued as multiple events, requiring more buffer
> space.  16 bytes is probably a conservative estimate of the longest 
> distance
> moved.
>
> - Why does the guest kernel (i8042_controller_check()) conclude that there 
> is
> no i8042 controller if it finds the queue to be full?  Reducing 
> PS2_QUEUE_SIZE
> to 16 is still not enough.  It need to be something less than 16 for the 
> guest
> kernel to successfully detect the controller.
>
> Interestingly, the problem is not seen on RHEL 5.3.  It leaves the mouse
> disabled on shutdown via AUX_DISABLE_DEV mouse command.  AUX_DISABLE_DEV
> command resets MOUSE_STATUS_ENABLED flag in PS2MouseState->mouse_status, 
> which
> makes mouse events to be dropped by ps2_mouse_event().
>
> On SLES 11, however, mouse is disabled but then it is again re-enabled 
> (via
> AUX_ENABLE_DEV) prior to resetting the processor, which leaves the mouse
> enabled during BIOS.  Not clear what makes the guest re-enable the mouse 
> on
> shutdown.
>
> Folks have some clues on the right way to address this?
>

Sorry for the duplicate message above (mail server was taking hours to post, 
and I got impatient...)

Changing PS2_QUEUE_SIZE to 15 and the "reserved space" to 8 fixes the 
problem for me:

diff --git a/hw/ps2.c b/hw/ps2.c
index fb77005..51a3ab8 100644
--- a/hw/ps2.c
+++ b/hw/ps2.c
@@ -70,7 +70,7 @@
 #define MOUSE_STATUS_ENABLED    0x20
 #define MOUSE_STATUS_SCALE21    0x10

-#define PS2_QUEUE_SIZE 256
+#define PS2_QUEUE_SIZE 15

 typedef struct {
     uint8_t data[PS2_QUEUE_SIZE];
@@ -346,7 +346,7 @@ static void ps2_mouse_event(void *opaque,
     s->mouse_buttons = buttons_state;

     if (!(s->mouse_status & MOUSE_STATUS_REMOTE) &&
-        (s->common.queue.count < (PS2_QUEUE_SIZE - 16))) {
+        (s->common.queue.count < (PS2_QUEUE_SIZE - 8))) {
         for(;;) {
             /* if not remote, send event. Multiple events are sent if
                too big deltas */

Both keyboard and mouse remain responsive after reboot, no matter how much I 
type / move the mouse during reboot.

Any comments?

Thanks,
Dinesh Subhraveti