Re: [PATCH v12 01/20] target/riscv: expose *envcfg csr and priv to qemu-user as well

[Richard Henderson <richard.henderson@linaro.org>]

On 8/30/24 09:34, Deepak Gupta wrote:
> Execution environment config CSR controlling user env and current
> privilege state shouldn't be limited to qemu-system only. *envcfg
> CSRs control enabling of features in next lesser mode. In some cases
> bits *envcfg CSR can be lit up by kernel as part of kernel policy or
> software (user app) can choose to opt-in by issuing a system call
> (e.g. prctl). In case of qemu-user, it should be no different because
> qemu is providing underlying execution environment facility and thus
> either should provide some default value in *envcfg CSRs or react to
> system calls (prctls) initiated from application. priv is set to PRV_U
> and menvcfg/senvcfg set to 0 for qemu-user on reest.
> 
> `henvcfg` has been left for qemu-system only because it is not expected
> that someone will use qemu-user where application is expected to have
> hypervisor underneath which is controlling its execution environment. If
> such a need arises then `henvcfg` could be exposed as well.
> 
> Relevant discussion:
> https://lore.kernel.org/all/ 
> CAKmqyKOTVWPFep2msTQVdUmJErkH+bqCcKEQ4hAnyDFPdWKe0Q@mail.gmail.com/
> 
> Signed-off-by: Deepak Gupta<debug@rivosinc.com>
> Suggested-by: Richard Henderson<richard.henderson@linaro.org>
> Reviewed-by: Alistair Francis<alistair.francis@wdc.com>
> ---
>   target/riscv/cpu.c | 5 +++++
>   target/riscv/cpu.h | 9 +++++----
>   2 files changed, 10 insertions(+), 4 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~