Re: [Xen-devel] regression from 22242:7831b8e5aae2 (x86 guest pagetable walker: check for invalid bits in pagetable entries)?

[Tim Deegan <tim@xxxxxxx>]

At 16:58 +0000 on 17 Feb (1329497937), Jan Beulich wrote:
> >>> On 17.02.12 at 17:23, Tim Deegan <tim@xxxxxxx> wrote:
> > At 15:50 +0000 on 17 Feb (1329493838), Jan Beulich wrote:
> >> The problem appears to be that the or-ing in of PFEC_reserved_bit
> >> happens without consideration of PFEC_present. If you can confirm
> >> I'm not mis-interpreting things, fixing this should be relatively
> >> strait forward (though the question would be whether it should be
> >> guest_walk_tables() or its callers that should be fixed).
> > 
> > We should fix it in guest_walk_tables, since AFAICS it's possible for
> > PFEC_reserved_bit to be set based on a bad higher-level entry even if a
> > lower-level one has _PAGE_PRESENT clear.
> > 
> > Something like the attached (compile-tested only) patch? 
> 
> That was really fast, thanks!
> 
> Yes, that looks like it should do it. We'll want to give it a try early
> next week.

I've applied it, since it seemed not to break anything and I'll be away
from my test boxes for a while.  Let me know of you're still seeing any
problems. 

Cheers,

Tim.
 

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