Re: [PATCH v2 9/9] target/riscv: Use a smaller guess size for no-MMU PMP

[Bin Meng]

On Fri, May 8, 2020 at 3:29 AM Alistair Francis
 wrote:
>
> Signed-off-by: Alistair Francis 
> ---
>  target/riscv/pmp.c | 19 ++-
>  1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
> index 0e6b640fbd..5aba4d13ea 100644
> --- a/target/riscv/pmp.c
> +++ b/target/riscv/pmp.c
> @@ -233,12 +233,21 @@ bool pmp_hart_has_privs(CPURISCVState *env, 
> target_ulong addr,
>  return true;
>  }
>
> -/*
> - * if size is unknown (0), assume that all bytes
> - * from addr to the end of the page will be accessed.
> - */
>  if (size == 0) {
> -pmp_size = -(addr | TARGET_PAGE_MASK);
> +if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
> +/*
> + * if size is unknown (0), assume that all bytes
> + * from addr to the end of the page will be accessed.
> + */
> +pmp_size = -(addr | TARGET_PAGE_MASK);
> +} else {
> +/*
> + * If size is unknown (0) and we don't have an MMU,
> + * just guess the size as the xlen as we don't want to
> + * access an entire page worth.
> + */

It looks the comment does not match the code logic. This else branch
is the MMU branch.

> +pmp_size = sizeof(target_ulong);
> +}
>  } else {
>  pmp_size = size;
>  }
> --

Regards,
Bin

[PATCH v2 9/9] target/riscv: Use a smaller guess size for no-MMU PMP

[Alistair Francis]

Signed-off-by: Alistair Francis 
---
 target/riscv/pmp.c | 19 ++-
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index 0e6b640fbd..5aba4d13ea 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -233,12 +233,21 @@ bool pmp_hart_has_privs(CPURISCVState *env, target_ulong 
addr,
 return true;
 }
 
-/*
- * if size is unknown (0), assume that all bytes
- * from addr to the end of the page will be accessed.
- */
 if (size == 0) {
-pmp_size = -(addr | TARGET_PAGE_MASK);
+if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
+/*
+ * if size is unknown (0), assume that all bytes
+ * from addr to the end of the page will be accessed.
+ */
+pmp_size = -(addr | TARGET_PAGE_MASK);
+} else {
+/*
+ * If size is unknown (0) and we don't have an MMU,
+ * just guess the size as the xlen as we don't want to
+ * access an entire page worth.
+ */
+pmp_size = sizeof(target_ulong);
+}
 } else {
 pmp_size = size;
 }
-- 
2.26.2