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

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

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