Re: [v8][PATCH 06/16] hvmloader/pci: disable all pci devices conflicting with rdm

["Chen, Tiejun" <tiejun.chen@intel.com>]

Jan and George,

That implementation to this problem in v7 is really not accepted? Yes, 
that isn't a best solution to make our original mechanism very well, but 
in high level I just think that should be a correct solution fixing this 
problem. According to recent discussion seems we have not a efficient 
way which can be put into 4.6. So instead, could your guys help me make 
that better gradually to reach our current requirement as possible?

Thanks
Tiejun

On 2015/7/17 0:40, George Dunlap wrote:
> On 07/16/2015 05:08 PM, Chen, Tiejun wrote:
>> On 2015/7/16 23:39, George Dunlap wrote:
>>> On 07/16/2015 04:20 PM, Chen, Tiejun wrote:
>>>>>> What about this?
>>>>>
>>>>> Looks reasonable (but don't forget that I continue to be unconvinced
>>>>> that the patch as a whole makes sense).
>>>>
>>>> Yes, I always keep this in my mind as I mentioned in patch #00. Any risk
>>>> you're still concerning? Is it that case if guest OS force enabling
>>>> these devices again? IMO, at this point there are two cases:
>>>>
>>>> #1. Without passing through a RMRR device
>>>>
>>>> Those emulated devices don't create 1:1 mapping so its safe, right?
>>>>
>>>> #2. With passing through a RMRR device
>>>>
>>>> This just probably cause these associated devices not to work well, but
>>>> still don't bring any impact to other Domains, right? I mean this isn't
>>>> going to worsen the preexisting situation.
>>>>
>>>> If I'm wrong please correct me.
>>>
>>> But I think the issue is, without doing *something* about MMIO
>>> collisions, the feature as a whole is sort of pointless.  You can
>>> carefully specify rdm="strategy=host,reserved=strict", but you might
>>
>> I got what your mean. But there's no a good approach to bridge between
>> xl and hvmloader to follow this policy. Right now, maybe just one thing
>> could be tried like this,
>>
>> Under hvmloader circumstance,
>>
>> "strict" -> Still set RDM as E820_RESERVED
>> "relaxed" -> Set RDM as a new internal E820 flag like E820_HAZARDOUS
>>
>> Then in the case of MMIO collisions
>>
>> E820_RESERVED -> BUG() -> Stop VM
>> E820_HAZARDOUS -> our warning messages + disable devices
>>
>> I think this can make sure we always take consistent policy in each
>> involved cycle.
>
> A better way to communicate between xl and hvmloader is to use xenstore,
> as we do for allow_memory_reallocate.  But I have very little hope we
> can hash out a suitable design for that by tomorrow.
>
>   -George
>
>