Re: [Qemu-devel] [SeaBIOS] [RFC PATCH] Distinguish between reset types

[H. Peter Anvin]

On 02/20/2013 07:37 AM, David Woodhouse wrote:
> On Wed, 2013-02-20 at 16:34 +0100, Paolo Bonzini wrote:
>> Il 20/02/2013 16:18, Laszlo Ersek ha scritto:
>>>>> I'm beginning to wish I'd just ignored the fact that
>>>>> we need a properly working "soft" reset to get back from 286 protected
>>>>> mode to real mode, and wired up the damn PAM reset unconditionally. I'm
>>>>> not convinced that the protected->real mode transition will work for
>>>>> anyone anyway.
>>> I believe currently we must be somewhere "between" soft reset & hard
>>> reset. I estimate getting closer to a well-emulated hard reset is more
>>> important than getting closer to a soft one. If you were to extend the
>>> i440FX reset handler so that it unconditionally resets the PAMs, I'd
>>> give my Rb. (Take it for what it's worth :))
>>
>> It would actually make sense.  The right way to do soft reset has
>> nothing to do with qemu_system_reset_request().
> 
> I've posted that version of the patch, with a suitable comment.
> 

Right... the "soft reset" described above is really INIT, which isn't
even a reset in modern CPUs (it couldn't be, it has to preserve caches)
but more of a special interrupt.  It is also used during multiprocessor
init.

        -hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.