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

Anup Patel
2023-03-23T12:18:40Z

Hi Alex,

On Thu, Mar 16, 2023 at 6:48 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
>
> 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