[PATCH v2 00/10] Introduce sv48 support without relocatable kernel

Alexandre Ghiti
2021-09-29T14:51:40Z

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.

Tested on:
- qemu rv64 sv39: OK
- qemu rv64 sv48: OK
- qemu rv64 sv39 + kasan: OK
- qemu rv64 sv48 + kasan: OK
- qemu rv32: OK
- Unmatched: OK

Changes in v2:
- Rebase onto for-next
- Fix KASAN
- Fix stack canary
- Get completely rid of MAXPHYSMEM configs
- Add documentation

Alexandre Ghiti (10):
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

Documentation/riscv/vm-layout.rst | 36 ++
arch/riscv/Kconfig | 35 +-
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 | 2 +-
arch/riscv/include/asm/page.h | 10 +
arch/riscv/include/asm/pgalloc.h | 40 +++
arch/riscv/include/asm/pgtable-64.h | 108 +++++-
arch/riscv/include/asm/pgtable.h | 30 +-
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 | 323 +++++++++++++++---
arch/riscv/mm/kasan_init.c | 91 +++--
drivers/firmware/efi/libstub/efi-stub.c | 2 +
include/asm-generic/pgalloc.h | 24 +-
include/linux/sizes.h | 1 +
21 files changed, 615 insertions(+), 131 deletions(-)

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2.30.2