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

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

> On 19 Mar 2025, at 12:18, Luca Fancellu <Luca.Fancellu@xxxxxxx> wrote:
> 
> Hi Jan,
> 
>> On 19 Mar 2025, at 11:35, Jan Beulich <jbeulich@xxxxxxxx> 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?
> 
> sorry I’m not a RISC-V expert, I saw the stub and I thought the architecture 
> wanted to have them implemented.
> 
> If not, is it possible to let the RISC-V people handle that separately? I’ll 
> be off until 31st of March and this patch is
> useful for Ayan to introduce a building status for arm32.

Oh, apologies I didn’t see you were replying to Oleksii, anyway if possible and 
you are ok with this patch,
I would ask the above.

> 
> Cheers,
> Luca
> 
>> 
>> Jan
>