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

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxx>
>>
>>
>>   
>>> Keir Fraser wrote:
>>>     
>>>> On 21/01/2010 10:19, "Weidong Han" <weidong.han@xxxxxxxxx> 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@xxxxxxxxx>
>>>     
>>
>>   






-- 
Best regards,
 Sander                            mailto:linux@xxxxxxxxxxxxxx


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