Re: [PATCH v9 3/5] riscv: Allow user to set the satp mode

[Bin Meng]

On Tue, Jan 31, 2023 at 11:13 PM Alexandre Ghiti <alexghiti@rivosinc.com> wrote:
>
> RISC-V specifies multiple sizes for addressable memory and Linux probes for
> the machine's support at startup via the satp CSR register (done in
> csr.c:validate_vm).
>
> As per the specification, sv64 must support sv57, which in turn must
> support sv48...etc. So we can restrict machine support by simply setting the
> "highest" supported mode and the bare mode is always supported.
>
> You can set the satp mode using the new properties "sv32", "sv39", "sv48",
> "sv57" and "sv64" as follows:
> -cpu rv64,sv57=on  # Linux will boot using sv57 scheme
> -cpu rv64,sv39=on  # Linux will boot using sv39 scheme
> -cpu rv64,sv57=off # Linux will boot using sv48 scheme
> -cpu rv64          # Linux will boot using sv57 scheme by default
>
> We take the highest level set by the user:
> -cpu rv64,sv48=on,sv57=on # Linux will boot using sv57 scheme
>
> We make sure that invalid configurations are rejected:
> -cpu rv64,sv39=off,sv48=on # sv39 must be supported if higher modes are
>                            # enabled
>
> We accept "redundant" configurations:
> -cpu rv64,sv48=on,sv57=off # Linux will boot using sv48 scheme
>
> And contradictory configurations:
> -cpu rv64,sv48=on,sv48=off # Linux will boot using sv39 scheme
>
> Co-Developed-by: Ludovic Henry <ludovic@rivosinc.com>
> Signed-off-by: Ludovic Henry <ludovic@rivosinc.com>
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> ---
>  target/riscv/cpu.c | 207 +++++++++++++++++++++++++++++++++++++++++++++
>  target/riscv/cpu.h |  19 +++++
>  target/riscv/csr.c |  12 ++-
>  3 files changed, 231 insertions(+), 7 deletions(-)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>