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Re: [PATCH v2 2/6] x86/P2M: relax permissions of PVH Dom0's MMIO entries

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Mon, 6 Sep 2021 17:55:59 +0200
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  • Cc: Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Mon, 06 Sep 2021 15:56:07 +0000
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On 06.09.2021 17:48, Andrew Cooper wrote:
> On 02/09/2021 09:33, Jan Beulich wrote:
>> To become independent of the sequence of mapping operations, permit
>> "access" to accumulate for Dom0, noting that there's not going to be an
>> introspection agent for it which this might interfere with. While e.g.
>> ideally only ROM regions would get mapped with X set, getting there is
>> quite a bit of work.
> ?
> That's literally the opposite of what needs to happen to fix this bug. 
> Introspection is the only interface which should be restricting X
> permissions.

What agent would be handling access violations in Dom0? The description
(now) focuses on entirely Dom0; I agree that DomU wants things the way
you describe (provided all p2m_access_t abuses are gone).




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