From mboxrd@z Thu Jan  1 00:00:00 1970
From: Weidong Han <weidong.han@intel.com>
Subject: Re: [PATCH][RFC] gfx_passthru: warning when vgabios rom
 has invalid checksum
Date: Mon, 22 Feb 2010 16:56:37 +0800
Message-ID: <4B8246C5.4090005@intel.com>
References: <4B8219F1.5040301@jp.fujitsu.com> <4B823088.8090706@intel.com>
	<4B82398B.6020109@jp.fujitsu.com>
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To: Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, "Ian.Jackson@eu.citrix.com" <Ian.Jackson@eu.citrix.com>
List-Id: xen-devel@lists.xenproject.org

Noboru Iwamatsu wrote:
> Hi,
>
>  >> Intel DX58SO + GeForce GTS250:	checksum is OK.
>  >> Intel DX58SO + GeForce 9600GT:	checksum is OK.
>  >> Fujitsu Q35 M/B + IGD:		checksum is bad.
>  >>
>  > What does "checksum is bad" mean here?
>
> It means shadowed VGABIOS has invalid checksum
> and requires recalculating.
>
>  >> What do you think, Weidong?
>  >> Is just warning enough? Or, should we stop loading the rom?
>  >>
>  >>
>  > Does it still work or not when checksum is bad? If it works, we should
>  > not stop loading the rom.
>
> When the checksum is bad,
> if it is not recalculated, guest has some trouble about handling the
> VGA (unable to show BIOS screen, unable to load the gfx driver
> properly, ...).
For this case, it's reasonable to warning and stop loading rom. We 
didn't encounter this issue.
> If it is recalculated, it seems to work fine.
>   
How did you recalculate it? is it possible to recalculate it when detect 
invalid checksum?

Regards,
Weidong

> Regards,
> Noboru.
>
>   
>> Noboru Iwamatsu wrote:
>>     
>>> Hi,
>>>
>>> According to the "PCI Firmware Spec Rev 3.0",
>>> the system firmware have to write the new checksum after resizing
>>> the expansion ROM area.
>>>
>>> So, when re-using the shadowed VGABIOS, the checksum must
>>> be valid, and if it is invalid, we should consider the BIOS has
>>> a bug or memory area is corrupted.
>>>
>>> This patch just add the warning message when checksum requires
>>> recalculation.
>>>
>>> I tried this following environments.
>>>
>>> Intel DX58SO + GeForce GTS250:	checksum is OK.
>>> Intel DX58SO + GeForce 9600GT:	checksum is OK.
>>> Fujitsu Q35 M/B + IGD:		checksum is bad.
>>>
>>>       
>> What does "checksum is bad" mean here?
>>     
>>> What do you think, Weidong?
>>> Is just warning enough? Or, should we stop loading the rom?
>>>
>>>
>>>       
>> Does it still work or not when checksum is bad? If it works, we should
>> not stop loading the rom.
>>
>> Regards,
>> Weidong
>>     
>>> Regards,
>>> Noboru.
>>>
>>>       
>
>
>