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Re: [PATCH 1/4] xen/xsm: Add XSM_HW_PRIV
- To: Jason Andryuk <jason.andryuk@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 11 Jun 2025 15:02:12 +0200
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 11 Jun 2025 13:02:27 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 11.06.2025 00:57, Jason Andryuk wrote:
> Xen includes disctinct concepts of a control domain (privileged) and a
> hardware domain, but there is only a single XSM_PRIV check. For dom0
> this is not an issue as they are one and the same.
>
> With hyperlaunch and its build capabilities, a non-privileged hwdom and a
> privileged control domain should be possible. Today the hwdom fails the
> XSM_PRIV checks for hardware-related hooks which it should be allowed
> access to.
>
> Introduce XSM_HW_PRIV, and use it to mark many of the physdev_op and
> platform_op. The hwdom is allowed access for XSM_HW_PRIV.
>
> Make XSM_HW_PRIV a new privilege level that is given to the hardware
> domain, but is not exclusive. The control domain can still execute
> XSM_HW_PRIV commands. This is a little questionable since it's unclear
> how the control domain can meaningfully execute them. But this approach
> is chosen to maintain the increasing privileges and keep control domain
> fully privileged.
I consider this conceptually wrong. "Control" aiui refers to software
(e.g. VMs or system-wide settings), but there ought to be a (pretty?)
clear boundary between control and hardware domains, imo. As to
"pretty" - should any overlap be necessary (xms_machine_memory_map()
comes to mind), such would need handling specially then, I think. At
the same time: The more of an overlap there is, the less clear it is
why the two want/need separating in the first place.
Jan
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