Re: [Qemu-devel] [PATCH 4/3] wakeup: only reset the CPU

[Laszlo Ersek <lersek@redhat.com>]

On 03/05/13 20:25, Paolo Bonzini wrote:
> Il 05/03/2013 20:12, Laszlo Ersek ha scritto:
>> On 03/05/13 17:59, David Woodhouse wrote:> On Tue, 2013-03-05 at 17:03 +0100, Paolo Bonzini wrote:
>>>> Resuming from suspend-to-RAM should not reset all devices.  Only the
>>>> CPU should get a reset signal.
>>>
>>> Hm... on reflection, I don't actually know if this is true.
>>>
>>> Perhaps we *should* reset all devices. After all, in a real machine
>>> they'll all have been turned off and the RAM will have been in
>>> self-refresh. Surely they have to be reset?
>>>
>>> So maybe we should *let* the i440FX PAM registers get reset to point to
>>> ROM. And fix the firmware to *cope* with that, check to see if the
>>> shadow RAM already holds an image of a started-up firmware with the
>>> correct checksum, and jump back to it.
>>>
>>> That is: perhaps it's a *SeaBIOS* bug that suspend/resume doesn't work
>>> if the PAM configuration is reset?
>>
>> I think it is indeed a problem with SeaBIOS. Open romlayout.S: [...]
>>
>> It checks the CMOS only after looking at HaveRunPost. The value of
>> HaveRunPost depends on the PAM settings. It's always 0 in ROM, in which
>> case we continue at handle_post() [src/post.c].
> 
> Actually, Peter explained that it is okay.  S3 doesn't clear the PAM
> configuration, but S4 does.  The PAM registers are attached to the same
> power line as the RAM.

Ah, you expect me to understand that "memory controller configuration"
is a superset of the PAM registers :)

Laszlo