Re: [PATCH v1 6/6] xen/riscv: implement p2m mapping functionality

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.05.2025 17:57, Oleksii Kurochko wrote:
> These utilities are needed for building and managing RISC-V guest page
> tables and MMIO mappings by using functions map_regions_p2mt() and
> guest_physmap_add_entry().
> 
> To implement p2m mapping functionality the following is introduced:
> - Define P2M root level/order and entry count.
> - Introdude radix type for p2m types as it isn't enough free bits in pte
>   and the helpers (p2m_type_radix_{get,set}()) to deal with them.
> - Introduce p2m_is_*() helpers() as  pte_is_*() helpers are checking
>   the valid bit set in the PTE but we have to check p2m_type instead
>   (look at the comment above p2m_is_valid() for some details).

May I suggest to name them at least p2me_is_*() then, as they check entries
rather than entire P2Ms? Same perhaps elsewhere.

> - Introduce helper to set p2m's pte permission: p2m_set_permissions().
> - Introduce helper to create p2m entry based on mfn, p2m_type_t and
>   p2m_access_t.
> - Introduce helper to generate table entry with correct attributes:
>   page_to_p2m_table().
> - Introduce p2m page allocation function: p2m_alloc_page().
> - Introduce functions to write/remove p2m's entries: p2m_{write,remove}_pte().
> - Introduce function to allocate p2m table: p2m_create_table().
> - Introduce functions used to free p2m entry.
> - Introduce function for table walking: p2m_next_level().
> - Introduce function to insert an entry in the p2m (p2m_set_entry()).
> - Introduce superpage splitting: p2m_split_superpage()).
> - Introduce page table type defines (PGT_{none,writable_page}, etc).
> 
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> ---
>  xen/arch/riscv/include/asm/mm.h   |  32 +-
>  xen/arch/riscv/include/asm/p2m.h  |  17 +-
>  xen/arch/riscv/include/asm/page.h |  11 +
>  xen/arch/riscv/p2m.c              | 780 ++++++++++++++++++++++++++++++
>  4 files changed, 829 insertions(+), 11 deletions(-)

It's imo too many things you do in one go here.

Jan