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

[Anup Patel]

On Thu, Mar 23, 2023 at 6:24 PM Alexandre Ghiti <alexghiti at rivosinc.com> wrote:
>
> Hi Anup,
>
> On Thu, Mar 23, 2023 at 1:18 PM Anup Patel <apatel at ventanamicro.com> wrote:
> >
> > 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
>
> Hmmm I don't get that in any of my test configs, would you mind
> sharing yours and your qemu command line?

Try alexghiti_test branch at
https://github.com/avpatel/linux.git

I am building the kernel using defconfig and my rootfs is
based on busybox.

My QEMU command is:
qemu-system-riscv64 -M virt -m 512M -nographic -bios
opensbi/build/platform/generic/firmware/fw_dynamic.bin -kernel
./build-riscv64/arch/riscv/boot/Image -append "root=/dev/ram rw
console=ttyS0 earlycon" -initrd ./rootfs_riscv64.img -smp 4

Regards,
Anup

>
> 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
> > >