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

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

Noboru Iwamatsu wrote:
>  > So, I think RMRR that has no-existent device is valid.
>
> 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?

Regards,
Weidong
> Noboru.
>
>   
>> Hi,
>>
>> After registered invalid DRHDs, Xen hangs in boot time.
>>
>> About RMRR, I understood the logic.
>> In my mainboard, unfortunately, RMRR has non-existent device under
>> its scope, and to make matters worse, the RMRR range is invalid.
>> So, I think RMRR that has no-existent device is valid.
>>
>> How do you think about these?
>>
>>     
>>> Hi Noboru,
>>>
>>> You should not ignore DRHD even if devices under its scope are not pci
>>> discoverable. For the sake of security, we still enable these DRHDs
>>> but don't set any context mappings. In that case, any DMA that comes
>>> from these "supposedly disabled" devices will get blocked by VT-d, and
>>> hence avoid any security vulnerability with malicious s/w re-enabling
>>> these devices.
>>>
>>> You RMRR validity fixing is wrong. My RMRR patch is no problem. Pls
>>> note that the RMRR checking logic is:
>>> If all devices under RMRR's scope are not pci discoverable
>>> Ignore the RMRR
>>> Else if base_address> end_address
>>> Return error
>>> Else
>>> Register RMRR
>>>
>>> Regards,
>>> Weidong
>>>
>>>
>>> -----Original Message-----
>>> From: Noboru Iwamatsu [mailto:n_iwamatsu@jp.fujitsu.com]
>>> Sent: Thursday, January 21, 2010 4:26 PM
>>> To: Han, Weidong
>>> Cc: xen-devel@lists.xensource.com; keir.fraser@eu.citrix.com
>>> Subject: Re: [Xen-devel] [PATCH] VT-d: improve RMRR validity checking
>>>
>>> Hi,
>>>
>>> Some Q35 mainboard that has buggy BIOS, I have one of this, reports
>>> invalid DRHD in addition to the invalid RMRR.
>>>
>>> Attached patch fixes this DRHD issue in the same way as RMRR.
>>> And also, I fixed RMRR validity checking loop.
>>>
>>> Noboru.
>>>
>>> Signed-off-by: Noboru Iwamatsu<n_iwamatsu@jp.fujitsu.com>
>>>
>>>
>>> -------- Original Message --------
>>> Subject: [Xen-devel] [PATCH] VT-d: improve RMRR validity checking
>>> From: Han, Weidong<weidong.han@intel.com>
>>> To: xen-devel@lists.xensource.com<xen-devel@lists.xensource.com>
>>> Date: Thu Jan 21 2010 11:46:12 GMT+0900
>>>
>>>       
>>>> Currently, Xen checks RMRR range and disables VT-d if RMRR range is
>>>> set incorrectly in BIOS rigorously. But, actually we can ignore the
>>>> RMRR if the device under its scope are not pci discoverable, because
>>>> the RMRR won't be used by non-existed or disabled devices.
>>>>
>>>> This patch ignores the RMRR if the device under its scope are not pci
>>>> discoverable, and only checks the validity of RMRRs that are actually
>>>> used. In order to avoid duplicate pci device detection code, this
>>>> patch defines a function pci_device_detect for it.
>>>>
>>>> Signed-off-by: Weidong Han<weidong.han@intel.com>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@lists.xensource.com
>>>> http://lists.xensource.com/xen-devel
>>>>         
>>
>> _______________________________________________
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>>     
>
>
>