On Wed, Aug 28, 2024 at 9:21 AM Deepak Gupta <debug@rivosinc.com> 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.
>
> `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>
Alistair
> ---
> target/riscv/cpu.h | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 87742047ce..270a2a031c 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -226,8 +226,12 @@ struct CPUArchState {
> uint32_t elf_flags;
> #endif
>
> -#ifndef CONFIG_USER_ONLY
> target_ulong priv;
> + /* CSRs for execution environment configuration */
> + uint64_t menvcfg;
> + target_ulong senvcfg;
> +
> +#ifndef CONFIG_USER_ONLY
> /* This contains QEMU specific information about the virt state. */
> bool virt_enabled;
> target_ulong geilen;
> @@ -429,12 +433,9 @@ struct CPUArchState {
> target_ulong upmmask;
> target_ulong upmbase;
>
> - /* CSRs for execution environment configuration */
> - uint64_t menvcfg;
> uint64_t mstateen[SMSTATEEN_MAX_COUNT];
> uint64_t hstateen[SMSTATEEN_MAX_COUNT];
> uint64_t sstateen[SMSTATEEN_MAX_COUNT];
> - target_ulong senvcfg;
> uint64_t henvcfg;
> #endif
> target_ulong cur_pmmask;
> --
> 2.44.0
>
>