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

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?


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.


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