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

["Orzel, Michal" <michal.orzel@xxxxxxx>]

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.

~Michal