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(-)