Re: [PATCH] xen/arm: XEN_DOMCTL_get_address_size hypercall support

[Demi Marie Obenour <demiobenour@gmail.com>]

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On 10/2/25 06:10, Andrew Cooper wrote:
> On 01/10/2025 9:01 pm, Milan Djokic wrote:
>> Signed-off-by: Milan Djokic <milan_djokic@epam.com>
>>
>> ---
>> XEN_DOMCTL_get_address_size hypercall is not implemented for arm (only for x86)
>> It would be useful to have this hypercall supported for arm64, in order to get
>> current guest addressing mode and also to verify that XEN_DOMCTL_set_address_size
>> performs switch to target addressing mode (instead of relying on its returned error code only).
> 
> Please don't copy this misfeature of x86 PV guests into ARM.
> 
> Letting domains be of variable bitness after domain create leads to a
> whole lot of bugs, many security relevant.
> 
> 32bit vs 64bit should be an input to domain_create(), not something that
> is edited after the domain has been constructed.

Does this mean that Xen guests cannot support multiarch?
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)

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