Re: [PATCH] riscv: Fix bug in setting pmpcfg CSR for RISCV64

[Alistair Francis]

On Sat, Aug 8, 2020 at 6:05 AM Hou Weiying <weiying_hou@outlook.com> wrote:
>
> First, sizeof(target_ulong) equals to 4 on riscv32, so this change
> does not change the function on riscv32. Second, sizeof(target_ulong)
> equals to 8 on riscv64, and 'reg_index * 8 + i' is not a legal
> pmp_index (we will explain later), which should be 'reg_index * 4 + i'.
>
> If the parameter reg_index equals to 2 (means that we will change the
> value of pmpcfg2, or the second pmpcfg on riscv64), then
> pmpcfg_csr_write(env, 2, val) will map write tasks to
> pmp_write_cfg(env, 2 * 8 + [0...7], val). However, no cfg csr is indexed
> by value 16 or 23 on riscv64, so we consider it as a bug.
>
> We are looking for constant (e.g., define a new constant named
> RISCV_WORD_SIZE) in QEMU to help others understand code better,
> but none was found. A possible good explanation of this literal is it is
> the minimum word length on riscv is 4 bytes (32 bit).
>
> Signed-off-by: Hongzheng-Li <Ethan.Lee.QNL@gmail.com>
> Signed-off-by: Hou Weiying <weiying_hou@outlook.com>
> Signed-off-by: Myriad-Dreamin <camiyoru@gmail.com>

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

Thanks!

Applied to riscv-to-apply.next

Alistair

> ---
>  target/riscv/pmp.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
> index 2a2b9f5363..b14feeb7da 100644
> --- a/target/riscv/pmp.c
> +++ b/target/riscv/pmp.c
> @@ -320,8 +320,7 @@ void pmpcfg_csr_write(CPURISCVState *env, uint32_t 
> reg_index,
>
>      for (i = 0; i < sizeof(target_ulong); i++) {
>          cfg_val = (val >> 8 * i)  & 0xff;
> -        pmp_write_cfg(env, (reg_index * sizeof(target_ulong)) + i,
> -            cfg_val);
> +        pmp_write_cfg(env, (reg_index * 4) + i, cfg_val);
>      }
>  }
>
> @@ -336,7 +335,7 @@ target_ulong pmpcfg_csr_read(CPURISCVState *env, uint32_t 
> reg_index)
>      target_ulong val = 0;
>
>      for (i = 0; i < sizeof(target_ulong); i++) {
> -        val = pmp_read_cfg(env, (reg_index * sizeof(target_ulong)) + i);
> +        val = pmp_read_cfg(env, (reg_index * 4) + i);
>          cfg_val |= (val << (i * 8));
>      }
>      trace_pmpcfg_csr_read(env->mhartid, reg_index, cfg_val);
> --
> 2.20.1
>
>