Re: [PATCH] VT-d: improve RMRR validity checking

[Weidong Han <weidong.han@intel.com>]

Keir Fraser wrote:
> If we want to keep iommu=1 as default, then it is unacceptable to fail to
> boot on a fairly wide range of modern systems. We have to warn-and-disable,
> partially or completely, unless iommu=force is specified. Or we need to
> revert to iommu=0 as the default.
>
> What do you think, Weidong?
>   
Yes. I agree to warn-and-disable for these BIOS issues, and consider 
security more when iommu=force. Therefore I will implement a patch based 
on Nororu's patch.

Regards,
Weidong

>  -- Keir
>
> On 21/01/2010 14:17, "Sander Eikelenboom" <linux@eikelenboom.it> wrote:
>
>   
>> Hello Weidong,
>>
>> The problem is most vendor's just don't fix it and ignore the problem
>> completely.
>> Most often hiding them selves behind: come back when it's a problem with
>> Microsoft Windows, that the only single thing we support (and no other
>> software, so no vmware, no xen, no linux, perhaps even no hypervisor)
>> Well I don't know if the virtual pc in windows 7 supports an iommu now, but it
>> didn't in the past as far as i know, so any complain bounces off, and there it
>> all seems to end for them.
>>
>> Besides that i don't know if they do know what the problems with there
>> implementation in BIOS is when someone reports it.
>> I think some behind the scenes pressure from Intel to vendors might help to
>> solve some of them.
>> (my Q35 chipset, "Intel V-PRO" marketed motherboard (so much for that) also
>> suffers RMRR problem when another graphics card is inserted which switches off
>> the IGD).
>>
>> Although i think in my case your patch will work around that for me. Perhaps a
>> third option is needed, which does all the workarounds possible and warns
>> about potential security problem when requested ?
>>
>> --
>> Sander
>>
>>
>>
>>
>>
>>
>> Thursday, January 21, 2010, 1:46:39 PM, you wrote:
>>
>>     
>>> Noboru Iwamatsu wrote:
>>>       
>>>> Hi Weidong,
>>>>
>>>> I re-send the DRHD-fix patch.
>>>>
>>>> If DRHD does not have existent devices, ignore it.
>>>> If DRHD has both existent and non-existent devices, consider it invalid
>>>> and not register.
>>>>   
>>>>         
>>> Although you patch workarounds your buggy BIOS, but we still need to
>>> enable it for security purpose as I mentioned in previous mail. We
>>> needn't workaround / fix all BIOS issues in software. I think security
>>> is more important for this specific BIOS issue. Did you report the BIOS
>>> issue to your OEM vendor? maybe it's better to get it fixed in BIOS.
>>>       
>>> Regards,
>>> Weidong
>>>       
>>>> According to this patch and yours, my machine successfully booted
>>>> with vt-d enabled.
>>>>
>>>> Signed-off-by: Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>
>>>>
>>>>
>>>>   
>>>>         
>>>>> Keir Fraser wrote:
>>>>>     
>>>>>           
>>>>>> On 21/01/2010 10:19, "Weidong Han" <weidong.han@intel.com> wrote:
>>>>>>
>>>>>>       
>>>>>>             
>>>>>>>> Sorry this is typo.
>>>>>>>> I mean:
>>>>>>>> So, I think RMRR that has no-existent device is "invalid"
>>>>>>>> and whole RMRR should be ignored.
>>>>>>>>           
>>>>>>>>                 
>>>>>>> looks reasonable.
>>>>>>>
>>>>>>> Keir, I Acks Noboru's rmrr patch. Or do you want us to merge them to one
>>>>>>> patch?
>>>>>>>         
>>>>>>>               
>>>>>> Merge them up, re-send with both sign-off and acked-by all in one email.
>>>>>>
>>>>>> Thanks,
>>>>>> Keir
>>>>>>
>>>>>>       
>>>>>>             
>>>>> Sorry, I disagree with Noboru after thinking it again. If the RMRR has
>>>>> both no-existent device and also has existent devices in its scope, we
>>>>> should not ignore it because the existent devices under its scope will
>>>>> be impacted without the RMRR. so I suggest to print a warning instead of
>>>>> ignore it. Attached a patch for it.
>>>>>
>>>>> Signed-off-by: Weidong Han <weidong.han@intel.com>
>>>>>     
>>>>>           
>>>>   
>>>>         
>>
>>
>>
>>     
>
>
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