[PATCH v3] target/riscv: pmp: Ignore writes when RW=01

[PATCH v3] target/riscv: pmp: Ignore writes when RW=01

[Mayuresh Chitale]

As per the Priv spec: "The R, W, and X fields form a collective WARL
field for which the combinations with R=0 and W=1 are reserved."
However currently such writes are not ignored as ought to be. The
combinations with RW=01 are allowed only when the Smepmp extension
is enabled and mseccfg.MML is set.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
---
Changes in v3:
====
- Rebase on latest riscv-to-apply.next
- Add reviewed-by

Changes in v2:
====
- Default RW to 00 in case of an illegal value

 target/riscv/pmp.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index 4dfaa28fce2..162e88a90a6 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -123,6 +123,11 @@ static bool pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
         if (locked) {
             qemu_log_mask(LOG_GUEST_ERROR, "ignoring pmpcfg write - locked\n");
         } else if (env->pmp_state.pmp[pmp_index].cfg_reg != val) {
+            /* If !mseccfg.MML then ignore writes with encoding RW=01 */
+            if ((val & PMP_WRITE) && !(val & PMP_READ) &&
+                !MSECCFG_MML_ISSET(env)) {
+                val &= ~(PMP_WRITE | PMP_READ);
+            }
             env->pmp_state.pmp[pmp_index].cfg_reg = val;
             pmp_update_rule_addr(env, pmp_index);
             return true;
-- 
2.34.1

Re: [PATCH v3] target/riscv: pmp: Ignore writes when RW=01

[Alistair Francis]

On Thu, Oct 19, 2023 at 4:57 PM Mayuresh Chitale
<mchitale@ventanamicro.com> wrote:
>
> As per the Priv spec: "The R, W, and X fields form a collective WARL
> field for which the combinations with R=0 and W=1 are reserved."
> However currently such writes are not ignored as ought to be. The
> combinations with RW=01 are allowed only when the Smepmp extension
> is enabled and mseccfg.MML is set.
>
> Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
> Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Thanks!

Applied to riscv-to-apply.next

Alistair

> ---
> Changes in v3:
> ====
> - Rebase on latest riscv-to-apply.next
> - Add reviewed-by
>
> Changes in v2:
> ====
> - Default RW to 00 in case of an illegal value
>
>  target/riscv/pmp.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
> index 4dfaa28fce2..162e88a90a6 100644
> --- a/target/riscv/pmp.c
> +++ b/target/riscv/pmp.c
> @@ -123,6 +123,11 @@ static bool pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
>          if (locked) {
>              qemu_log_mask(LOG_GUEST_ERROR, "ignoring pmpcfg write - locked\n");
>          } else if (env->pmp_state.pmp[pmp_index].cfg_reg != val) {
> +            /* If !mseccfg.MML then ignore writes with encoding RW=01 */
> +            if ((val & PMP_WRITE) && !(val & PMP_READ) &&
> +                !MSECCFG_MML_ISSET(env)) {
> +                val &= ~(PMP_WRITE | PMP_READ);
> +            }
>              env->pmp_state.pmp[pmp_index].cfg_reg = val;
>              pmp_update_rule_addr(env, pmp_index);
>              return true;
> --
> 2.34.1
>
>