Re: [PATCH v7 0/4] riscv: Use PUD/P4D/PGD pages for the linear mapping

[Anup Patel <anup@brainfault.org>]

On Fri, Mar 10, 2023 at 3:15 PM Alexandre Ghiti <alexghiti@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
>
> 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

This works fine on QEMU RV64. I have tested on QEMU RV64 with
busybox and Fedora rootfs. I also tested KVM RV64 which works
fine as well.

But, QEMU RV32 with busybox rootfs is broken so you might want
to try that.

In any case, I have reviewed and tested this series at my end.

Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

>
>  arch/arm64/mm/mmu.c           |  4 ++--
>  arch/riscv/include/asm/page.h | 19 +++++++++++++++--
>  arch/riscv/mm/init.c          | 39 ++++++++++++++++++++++++++---------
>  arch/riscv/mm/physaddr.c      | 16 ++++++++++++++
>  drivers/of/fdt.c              | 11 +++++-----
>  include/linux/memblock.h      |  1 +
>  mm/memblock.c                 | 22 +++++++++++++++++++-
>  7 files changed, 92 insertions(+), 20 deletions(-)
>
> --
> 2.37.2
>