Re: [PATCH v4] riscv/gdbstub: add V bit to priv reg

[Alistair Francis]

On Mon, Dec 16, 2024 at 7:38 AM Yanfeng Liu <yfliu2008@qq.com> wrote:
>
> This adds virtualization mode (V bit) as bit(2) of register `priv`
> per RiscV debug spec v1.0.0-rc4. Checked with gdb-multiarch v12.1.
>
> Note that GDB may display `INVALID` tag for `priv` reg when V bit
> is set, this doesn't affect actual access to the bit though.
>
> Signed-off-by: Yanfeng Liu <yfliu2008@qq.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/gdbstub.c | 23 +++++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/target/riscv/gdbstub.c b/target/riscv/gdbstub.c
> index c07df972f1..18e88f416a 100644
> --- a/target/riscv/gdbstub.c
> +++ b/target/riscv/gdbstub.c
> @@ -213,7 +213,10 @@ static int riscv_gdb_get_virtual(CPUState *cs, 
> GByteArray *buf, int n)
>          RISCVCPU *cpu = RISCV_CPU(cs);
>          CPURISCVState *env = &cpu->env;
>
> -        return gdb_get_regl(buf, env->priv);
> +        /* Per RiscV debug spec v1.0.0 rc4 */
> +        target_ulong vbit = (env->virt_enabled) ? BIT(2) : 0;
> +
> +        return gdb_get_regl(buf, env->priv | vbit);
>  #endif
>      }
>      return 0;
> @@ -226,10 +229,22 @@ static int riscv_gdb_set_virtual(CPUState *cs, uint8_t 
> *mem_buf, int n)
>          RISCVCPU *cpu = RISCV_CPU(cs);
>          CPURISCVState *env = &cpu->env;
>
> -        env->priv = ldtul_p(mem_buf) & 0x3;
> -        if (env->priv == PRV_RESERVED) {
> -            env->priv = PRV_S;
> +        target_ulong new_priv = ldtul_p(mem_buf) & 0x3;
> +        bool new_virt = 0;
> +
> +        if (new_priv == PRV_RESERVED) {
> +            new_priv = PRV_S;
> +        }
> +
> +        if (new_priv != PRV_M) {
> +            new_virt = (ldtul_p(mem_buf) & BIT(2)) >> 2;
>          }
> +
> +        if (riscv_has_ext(env, RVH) && new_virt != env->virt_enabled) {
> +            riscv_cpu_swap_hypervisor_regs(env);
> +        }
> +
> +        riscv_cpu_set_mode(env, new_priv, new_virt);
>  #endif
>          return sizeof(target_ulong);
>      }
> --
> 2.34.1
>
>