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

["Heiko Stübner" <heiko@sntech.de>]

Am Mittwoch, 29. September 2021, 16:51:03 CET schrieb Alexandre Ghiti:
> 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

On a beagleV (which supports only sv39) I've tested both the limit via
the mmu-type in the devicetree and also that the fallback works when
I disable the mmu-type in the dt, so

Tested-by: Heiko Stuebner <heiko@sntech.de>

>   
>                                                                                  
> 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(-)
> 
>