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Re: [PATCH v5 2/3] arm/mpu: Introduce `v8r_el1_msa` device tree property for domains
- To: Luca Fancellu <Luca.Fancellu@xxxxxxx>
- From: "Orzel, Michal" <michal.orzel@xxxxxxx>
- Date: Mon, 11 May 2026 12:59:23 +0200
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Harry Ramsey <Harry.Ramsey@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Mon, 11 May 2026 10:59:40 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 11-May-26 12:53, Luca Fancellu wrote:
> Hi Michal,
>
>>>>> +
>>>>> +static inline bool v8r_el1_msa_domain_sanitise_config(
>>>>> + const struct xen_domctl_createdomain *config)
>>>> Why can't this function be common? I can see 3 definitions (Arm64 MPU,
>>>> Arm32
>>>> MPU, MMU) but they do not have anything that would prevent from
>>>> generalizing
>>>> them in a single function.
>>>
>>> I can do a common one I think, just to be aligned, should the common one
>>> behaves as the current implementation?
>>>
>>> Arm64/32 MMU: Only v8r_el1_msa == XEN_DOMCTL_CONFIG_ARM_V8R_EL1_MSA_NONE
>>> allowed
>>> Arm64: Only v8r_el1_msa ==
>>> XEN_DOMCTL_CONFIG_ARM_V8R_EL1_MSA_{NONE,PMSA,VMSA} allowed
>>> Arm32: Only v8r_el1_msa == XEN_DOMCTL_CONFIG_ARM_V8R_EL1_MSA_{NONE,PMSA}
>>> allowed
>> What's the reason for allowing NONE for MPU here? None denotes property not
>> specified but at this point it should be set to a default.
>
> We treat NONE as PMSA on Armv8-R, so either NONE and PMSA are valid and lead
> to PMSA at EL1
NONE denotes property not set i.e. set a default. IMO at the place where we set
a default, NONE should be switched to PMSA. This is a cleaner solution than
giving two options the same meaning. Sanitization could then verify that indeed
the default setting took place.
~Michal
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