On Sun, Jul 10, 2022 at 6:30 PM Weiwei Li <liwei...@iscas.ac.cn> wrote:
>
> Just add 1 to the effective privledge level when in HS mode, then reuse the
> check
> 'effective_priv < csr_priv' in riscv_csrrw_check to replace the privilege
> level
> related check in hmode. Then, hmode will only check whether H extension is
> supported.
>
> when accessing Hypervior CSRs:
> 1) if access from M privilege level, the check of 'effective_priv <
> csr_priv'
> passes, returns hmode(...) which will return RISCV_EXCP_ILLEGAL_INST when H
> extension is not supported and return RISCV_EXCP_NONE otherwise.
> 2) if access from HS privilege level, effective_priv will add 1, the check
> passes too, also returns hmode(...) too.
> 3) if access from VS/VU privilege level, the check fails, and returns
> RISCV_EXCP_VIRT_INSTRUCTION_FAULT
> 4) if access from U privilege level, the check fails, and returns
> RISCV_EXCP_ILLEGAL_INST
>
> Signed-off-by: Weiwei Li <liwei...@iscas.ac.cn>
> Signed-off-by: Junqiang Wang <wangjunqi...@iscas.ac.cn>
Reviewed-by: Alistair Francis <alistair.fran...@wdc.com>
Alistair
> ---
> target/riscv/csr.c | 18 +++++-------------
> 1 file changed, 5 insertions(+), 13 deletions(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 975007f1ac..2b3ed94366 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -312,13 +312,7 @@ static int aia_smode32(CPURISCVState *env, int csrno)
> static RISCVException hmode(CPURISCVState *env, int csrno)
> {
> if (riscv_has_ext(env, RVH)) {
> - /* Hypervisor extension is supported */
> - if ((env->priv == PRV_S && !riscv_cpu_virt_enabled(env)) ||
> - env->priv == PRV_M) {
> - return RISCV_EXCP_NONE;
> - } else {
> - return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> - }
> + return RISCV_EXCP_NONE;
> }
>
> return RISCV_EXCP_ILLEGAL_INST;
> @@ -3280,13 +3274,11 @@ static inline RISCVException
> riscv_csrrw_check(CPURISCVState *env,
> #if !defined(CONFIG_USER_ONLY)
> int csr_priv, effective_priv = env->priv;
>
> - if (riscv_has_ext(env, RVH) && env->priv == PRV_S) {
> + if (riscv_has_ext(env, RVH) && env->priv == PRV_S &&
> + !riscv_cpu_virt_enabled(env)) {
> /*
> - * We are in either HS or VS mode.
> - * Add 1 to the effective privledge level to allow us to access the
> - * Hypervisor CSRs. The `hmode` predicate will determine if access
> - * should be allowed(HS) or if a virtual instruction exception
> should be
> - * raised(VS).
> + * We are in HS mode. Add 1 to the effective privledge level to
> + * allow us to access the Hypervisor CSRs.
> */
> effective_priv++;
> }
> --
> 2.17.1
>
>
