Re: [PATCH v3 00/13] Introduce sv48 support without relocatable kernel

[Alexandre Ghiti]

On Thu, Jan 20, 2022 at 5:18 AM Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:
>
> On Mon, 06 Dec 2021 02:46:44 PST (-0800), alexandre.ghiti@xxxxxxxxxxxxx wrote:
> > * Please note notable changes in memory layouts and kasan population *
> >
> > This patchset allows to have a single kernel for sv39 and sv48 without
> > being relocatable.
> >
> > The idea comes from Arnd Bergmann who suggested to do the same as x86,
> > that is mapping the kernel to the end of the address space, which allows
> > the kernel to be linked at the same address for both sv39 and sv48 and
> > then does not require to be relocated at runtime.
> >
> > This implements sv48 support at runtime. The kernel will try to
> > boot with 4-level page table and will fallback to 3-level if the HW does not
> > support it. Folding the 4th level into a 3-level page table has almost no
> > cost at runtime.
> >
> > Note that kasan region had to be moved to the end of the address space
> > since its location must be known at compile-time and then be valid for
> > both sv39 and sv48 (and sv57 that is coming).
> >
> > Tested on:
> >   - qemu rv64 sv39: OK
> >   - qemu rv64 sv48: OK
> >   - qemu rv64 sv39 + kasan: OK
> >   - qemu rv64 sv48 + kasan: OK
> >   - qemu rv32: OK
> >
> > Changes in v3:
> >   - Fix SZ_1T, thanks to Atish
> >   - Fix warning create_pud_mapping, thanks to Atish
> >   - Fix k210 nommu build, thanks to Atish
> >   - Fix wrong rebase as noted by Samuel
> >   - * Downgrade to sv39 is only possible if !KASAN (see commit changelog) *
> >   - * Move KASAN next to the kernel: virtual layouts changed and kasan population *
> >
> > Changes in v2:
> >   - Rebase onto for-next
> >   - Fix KASAN
> >   - Fix stack canary
> >   - Get completely rid of MAXPHYSMEM configs
> >   - Add documentation
> >
> > Alexandre Ghiti (13):
> >   riscv: Move KASAN mapping next to the kernel mapping
> >   riscv: Split early kasan mapping to prepare sv48 introduction
> >   riscv: Introduce functions to switch pt_ops
> >   riscv: Allow to dynamically define VA_BITS
> >   riscv: Get rid of MAXPHYSMEM configs
> >   asm-generic: Prepare for riscv use of pud_alloc_one and pud_free
> >   riscv: Implement sv48 support
> >   riscv: Use pgtable_l4_enabled to output mmu_type in cpuinfo
> >   riscv: Explicit comment about user virtual address space size
> >   riscv: Improve virtual kernel memory layout dump
> >   Documentation: riscv: Add sv48 description to VM layout
> >   riscv: Initialize thread pointer before calling C functions
> >   riscv: Allow user to downgrade to sv39 when hw supports sv48 if !KASAN
> >
> >  Documentation/riscv/vm-layout.rst             |  48 ++-
> >  arch/riscv/Kconfig                            |  37 +-
> >  arch/riscv/configs/nommu_k210_defconfig       |   1 -
> >  .../riscv/configs/nommu_k210_sdcard_defconfig |   1 -
> >  arch/riscv/configs/nommu_virt_defconfig       |   1 -
> >  arch/riscv/include/asm/csr.h                  |   3 +-
> >  arch/riscv/include/asm/fixmap.h               |   1
> >  arch/riscv/include/asm/kasan.h                |  11 +-
> >  arch/riscv/include/asm/page.h                 |  20 +-
> >  arch/riscv/include/asm/pgalloc.h              |  40 ++
> >  arch/riscv/include/asm/pgtable-64.h           | 108 ++++-
> >  arch/riscv/include/asm/pgtable.h              |  47 +-
> >  arch/riscv/include/asm/sparsemem.h            |   6 +-
> >  arch/riscv/kernel/cpu.c                       |  23 +-
> >  arch/riscv/kernel/head.S                      |   4 +-
> >  arch/riscv/mm/context.c                       |   4 +-
> >  arch/riscv/mm/init.c                          | 408 ++++++++++++++----
> >  arch/riscv/mm/kasan_init.c                    | 250 ++++++++---
> >  drivers/firmware/efi/libstub/efi-stub.c       |   2
> >  drivers/pci/controller/pci-xgene.c            |   2 +-
> >  include/asm-generic/pgalloc.h                 |  24 +-
> >  include/linux/sizes.h                         |   1
> >  22 files changed, 833 insertions(+), 209 deletions(-)
>
> Sorry this took a while.  This is on for-next, with a bit of juggling: a
> handful of trivial fixes for configs that were failing to build/boot and
> some merge issues.  I also pulled out that MAXPHYSMEM fix to the top, so
> it'd be easier to backport.  This is bigger than something I'd normally like to
> take late in the cycle, but given there's a lot of cleanups, likely some fixes,
> and it looks like folks have been testing this I'm just going to go with it.
>

Yes yes yes! That's fantastic news :)

> Let me know if there's any issues with the merge, it was a bit hairy.
> Probably best to just send along a fixup patch at this point.

I'm going to take a look at that now, and I'll fix anything that comes
up quickly :)

Thanks!

Alex

>
> Thanks!