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

[Alexandre Ghiti]

Hi Anup,

On Thu, Mar 23, 2023 at 1:18 PM Anup Patel <apatel@xxxxxxxxxxxxxxxx> wrote:
>
> Hi Alex,
>
> On Thu, Mar 16, 2023 at 6:48 PM Alexandre Ghiti <alexghiti@xxxxxxxxxxxx> 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

Hmmm I don't get that in any of my test configs, would you mind
sharing yours and your qemu command line?

Thanks

>
> 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
> >