[PATCH v8 0/4] riscv: Use PUD/P4D/PGD pages for the linear mapping

[Anup Patel]

Hi Alex,

On Thu, Mar 16, 2023 at 6:48 PM Alexandre Ghiti <alexghiti at rivosinc.com> wrote:
>
> This patchset intends to improve tlb utilization by using hugepages for
> the linear mapping.
>
> As reported by Anup in v6, when STRICT_KERNEL_RWX is enabled, we must
> take care of isolating the kernel text and rodata so that they are not
> mapped with a PUD mapping which would then assign wrong permissions to
> the whole region: it is achieved by introducing a new memblock API.
>
> Another patch makes use of this new API in arm64 which used some sort of
> hack to solve this issue: it was built/boot tested successfully.
>
> base-commit-tag: v6.3-rc1
>
> v8:
> - Fix rv32, as reported by Anup
> - Do not modify memblock_isolate_range and fixes comment, as suggested by Mike
> - Use the new memblock API for crash kernel too in arm64, as suggested by Andrew
> - Fix arm64 double mapping (which to me did not work in v7), but ends up not
>   being pretty at all, will wait for comments from arm64 reviewers, but
>   this patch can easily be dropped if they do not want it.
>
> v7:
> - Fix Anup bug report by introducing memblock_isolate_memory which
>   allows us to split the memblock mappings and then avoid to map the
>   the PUD which contains the kernel as read only
> - Add a patch to arm64 to use this newly introduced API
>
> v6:
> - quiet LLVM warning by casting phys_ram_base into an unsigned long
>
> v5:
> - Fix nommu builds by getting rid of riscv_pfn_base in patch 1, thanks
>   Conor
> - Add RB from Andrew
>
> v4:
> - Rebase on top of v6.2-rc3, as noted by Conor
> - Add Acked-by Rob
>
> v3:
> - Change the comment about initrd_start VA conversion so that it fits
>   ARM64 and RISCV64 (and others in the future if needed), as suggested
>   by Rob
>
> v2:
> - Add a comment on why RISCV64 does not need to set initrd_start/end that
>   early in the boot process, as asked by Rob
>
> Alexandre Ghiti (4):
>   riscv: Get rid of riscv_pfn_base variable
>   mm: Introduce memblock_isolate_memory
>   arm64: Make use of memblock_isolate_memory for the linear mapping
>   riscv: Use PUD/P4D/PGD pages for the linear mapping

Kernel boot fine on RV64 but there is a failure which is still not
addressed. You can see this failure as following message in
kernel boot log:
    0.000000] Failed to add a System RAM resource at 80200000

Regards,
Anup

>
>  arch/arm64/mm/mmu.c           | 25 +++++++++++------
>  arch/riscv/include/asm/page.h | 19 +++++++++++--
>  arch/riscv/mm/init.c          | 53 ++++++++++++++++++++++++++++-------
>  arch/riscv/mm/physaddr.c      | 16 +++++++++++
>  drivers/of/fdt.c              | 11 ++++----
>  include/linux/memblock.h      |  1 +
>  mm/memblock.c                 | 20 +++++++++++++
>  7 files changed, 119 insertions(+), 26 deletions(-)
>
> --
> 2.37.2
>