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Re: [PATCH 08/10] xen/arm: Rename setup_pagetables with a more generic name
- To: "Orzel, Michal" <michal.orzel@xxxxxxx>
- From: Luca Fancellu <Luca.Fancellu@xxxxxxx>
- Date: Thu, 13 Mar 2025 11:08:46 +0000
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Thu, 13 Mar 2025 11:09:09 +0000
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- Thread-topic: [PATCH 08/10] xen/arm: Rename setup_pagetables with a more generic name
> On 13 Mar 2025, at 11:02, Orzel, Michal <michal.orzel@xxxxxxx> wrote:
>
>
>
> On 13/03/2025 11:32, Luca Fancellu wrote:
>>
>>
>> Hi Michal,
>>
>>> On 13 Mar 2025, at 10:19, Orzel, Michal <michal.orzel@xxxxxxx> wrote:
>>>
>>>
>>>
>>> On 12/03/2025 14:52, Luca Fancellu wrote:
>>>>
>>>>
>>>> Rename the setup_pagetables function to setup_mappings in
>>>> order to be implemented also for MPU system that does not
>>>> have page tables.
>>>
>>> mappings is better than pagetables, so:
>>> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
>>>
>>> but I'd like to understand what will be implementation of setup_mappings for
>>> MPU. I suppose regions setup such that the following call to early_fdt_map
>>> can
>>> succeed and doing this in setup_mm is already too late?
>>
>> So on the MPU side, mappings are well defined in HW by registers, so we
>> don’t need to
>> allocate pagetables, so setup_mappings in reality will only prepare our
>> logical data structure
>> that tracks the MPU region state (few regions are already written by the asm
>> early code and
>> needs to be tracked).
>>
>> early_fdt_map won’t use this logical view of the MPU (as it’s called early),
>> it will use low level
>> API to access the MPU registers, like the early asm code did, basically to
>> map the DTB.
>>
>> Doing that, we ensure that the current code flow in start_xen can be reused
>> as it.
> Then the question is: can the MPU part be moved to setup_mm if early_fdt_map
> does not need setup_mappings? If so, we can avoid introducing a function with
> a
> name that is at least odd in MPU context and leave setup_pagetables only for
> MMU. Adding a function with not ideal name just for the sake of avoiding
> #ifdef
> MMU does not sound like a good idea for me.
>
> You can check with others on this one.
I think you are right, I could provide a stub implementation for
setup_pagetables()
on MPU since there are no pagetables and introduce earlier setup_mm which
will setup the datastructure.
I don’t think anyone will oppose to that, so if I don’t ear from anyone I will
drop this patch
and implement the above
>
> ~Michal
>
|
