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

[Jan Beulich <jbeulich@xxxxxxxx>]

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?

Jan