Re: [PATCH v3 6/7] xen: introduce Kconfig ARCH_PAGING_MEMPOOL

[Jan Beulich <jbeulich@xxxxxxxx>]

On 26.03.2025 10:59, Orzel, Michal wrote:
> On 26/03/2025 10:54, Jan Beulich wrote:
>> On 26.03.2025 10:39, Orzel, Michal wrote:
>>> On 20/03/2025 08:32, Jan Beulich wrote:
>>>> On 19.03.2025 17:31, Oleksii Kurochko wrote:
>>>>> On 3/19/25 12:35 PM, Jan Beulich wrote:
>>>>>> On 18.03.2025 14:05, Oleksii Kurochko wrote:
>>>>>>> On 3/17/25 9:07 PM, Luca Fancellu wrote:
>>>>>>>> From: Penny Zheng<Penny.Zheng@xxxxxxx>
>>>>>>>>
>>>>>>>> ARM MPU system doesn't need to use paging memory pool, as MPU memory
>>>>>>>> mapping table at most takes only one 4KB page, which is enough to
>>>>>>>> manage the maximum 255 MPU memory regions, for all EL2 stage 1
>>>>>>>> translation and EL1 stage 2 translation.
>>>>>>>>
>>>>>>>> Introduce ARCH_PAGING_MEMPOOL Kconfig common symbol, selected for Arm
>>>>>>>> MMU systems, x86 and RISC-V.
>>>>>>>>
>>>>>>>> Wrap the code inside 'construct_domU' that deal with p2m paging
>>>>>>>> allocation in a new function 'domain_p2m_set_allocation', protected
>>>>>>>> by ARCH_PAGING_MEMPOOL, this is done in this way to prevent polluting
>>>>>>>> the former function with #ifdefs and improve readability
>>>>>>>>
>>>>>>>> Introduce arch_{get,set}_paging_mempool_size stubs for architecture
>>>>>>>> with !ARCH_PAGING_MEMPOOL.
>>>>>>>>
>>>>>>>> Remove 'struct paging_domain' from Arm 'struct arch_domain' when the
>>>>>>>> field is not required.
>>>>>>>>
>>>>>>>> Signed-off-by: Penny Zheng<penny.zheng@xxxxxxx>
>>>>>>>> Signed-off-by: Wei Chen<wei.chen@xxxxxxx>
>>>>>>>> Signed-off-by: Luca Fancellu<luca.fancellu@xxxxxxx>
>>>>>>>> ---
>>>>>>>> v3 changes:
>>>>>>>>    - Introduced ARCH_PAGING_MEMPOOL instead of HAS_PAGING_MEMPOOL
>>>>>>>> v2 changes:
>>>>>>>>    - make Kconfig HAS_PAGING_MEMPOOL common
>>>>>>>>    - protect also "xen,domain-p2m-mem-mb" reading with 
>>>>>>>> HAS_PAGING_MEMPOOL
>>>>>>>>    - do not define p2m_teardown{_allocation} in this patch
>>>>>>>>    - change commit message
>>>>>>>> ---
>>>>>>>>    xen/arch/arm/Kconfig              |  1 +
>>>>>>>>    xen/arch/arm/dom0less-build.c     | 74 
>>>>>>>> ++++++++++++++++++++-----------
>>>>>>>>    xen/arch/arm/include/asm/domain.h |  2 +
>>>>>>>>    xen/arch/riscv/Kconfig            |  1 +
>>>>>>>>    xen/arch/x86/Kconfig              |  1 +
>>>>>>>>    xen/common/Kconfig                |  3 ++
>>>>>>>>    xen/include/xen/domain.h          | 17 +++++++
>>>>>>>>    7 files changed, 73 insertions(+), 26 deletions(-)
>>>>>>> For RISC-V:
>>>>>>>    Reviewed-by: Oleksii Kurochko<oleksii.kurochko@xxxxxxxxx>
>>>>>> Mind me asking then why RISC-V needs this at this point? The stubs surely
>>>>>> were added to address some build issue, not because they are actively
>>>>>> meaningful?
>>>>>
>>>>> Only because we have stubs and not to have redefinition compilation
>>>>> error. And, yes, they are not actively meaningful now, at least. I am
>>>>> okay with not enabling of this config for RISC-V but then seems to me we
>>>>> have to drop stubs in riscv/stubs.c. ~ Oleksii
>>>>
>>>> Well, I don't think it's "have to", but I agree that dropping them would
>>>> make sense then (and be desirable).
>>> @Jan, @Oleksii, is there anything blocking this patch to be committed (Luca
>>> question does not seem to be answered)? Other patches in the series are 
>>> ready to
>>> be merged.
>>
>> While I think Oleksii's reply has sufficiently clarified things, I still 
>> wonder:
>> What question of Luca are you referring to? There's none visible in context 
>> here
>> afaics. The two questions that are visible were raised by me, and answered by
>> Oleksii (also visible in context above). There was an implication to draw 
>> from
>> that, yes, which Oleksii has now made explicit in his reply to your mail.
> Sure thing. I'll clarify. Here Luca asks question to you if it is possible for
> RISCV guys to handle it afterwards:
> https://lore.kernel.org/xen-devel/D86D58F5-1EDD-4362-B163-5AD25C5DCC51@xxxxxxx/
> https://lore.kernel.org/xen-devel/F827A271-0E9B-4240-BB1E-C039E9EE5656@xxxxxxx/
> and you did not answer to these e-mails.

I simply saw no need after Oleksii had replied.

Jan