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Re: hardware domain and control domain separation


  • To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 24 Jun 2025 07:25:17 +0200
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  • Cc: jason.andryuk@xxxxxxx, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, ayankuma@xxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, demiobenour@xxxxxxxxx
  • Delivery-date: Tue, 24 Jun 2025 05:25:50 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 24.06.2025 00:51, Stefano Stabellini wrote:
> On Mon, 23 Jun 2025, Demi Marie Obenour wrote:
>> On 6/23/25 11:44, Jan Beulich wrote:
>>> On 21.06.2025 02:41, Stefano Stabellini wrote:
>>> Also a more fundamental question I was wondering about: If Control had
>>> full privilege, nothing else in the system ought to be able to interfere
>>> with it. Yet then how does that domain communicate with the outside
>>> world? It can't have PV or Virtio drivers after all. And even if its
>>> sole communication channel was a UART, Hardware would likely be able to
>>> interfere.
> 
> There are well-established methods for implementing domain-to-domain
> communication that are free from interference, such as using carefully
> defined rings on static shared memory. I believe one of these techniques
> involves placing the indexes on separate pages and mapping them
> read-only from one of the two domains.

How's that going to help with the backend refusing service, which I view
as one "method" of interference? Or else, what exactly does "interference"
mean in this context? (More generally, I think it is necessary to very
clearly define terminology used. Without such, words can easily mean
different things to different people.)

Jan



 


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