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Date: Mon, 14 Sep 2009 23:30:21 +0200
From: Paolo Bonzini <bonzini@gnu.org>
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Subject: [Qemu-devel] Re: [PATCH 0/4] Fix VMState design flaws
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To: Juan Quintela <quintela@redhat.com>
Cc: qemu-devel@nongnu.org

On 09/14/2009 10:50 PM, Juan Quintela wrote:
> Paolo Bonzini<bonzini@gnu.org>  wrote:
>>>     * Add version_id field to post_load().  Now we can assign default values
>>>       in post_load for old versions of the state (ps2_kbd as example).
>>
>> While this is a good idea, why don't we first reset the devices upon
>> load, which would also set the default values?...
>
> It is safe to do that unconditionally?
> If so, I am all for it.  We can:
> - add reset field to vmstate
> - add default values to some fields, if it makse sense (haven't yet
>    looked at reset code).

The PS2 reset is this:

static void ps2_common_reset(PS2State *s)
{
     PS2Queue *q;
     s->write_cmd = -1;
     q = &s->queue;
     q->rptr = 0;
     q->wptr = 0;
     q->count = 0;
     s->update_irq(s->update_arg, 0); // calls kbd_update_kbd_irq
}

static void ps2_kbd_reset(void *opaque)
{
     PS2KbdState *s = (PS2KbdState *) opaque;

     ps2_common_reset(&s->common);
     s->scan_enabled = 0;
     s->translate = 0;
     s->scancode_set = 0;
}

All of these are later reset by load.  The update_irq may seem unsafe, 
but maybe deasserting an IRQ is better than leaving it in whatever state 
it was left by the previous VM...

Paolo