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[PATCH v3] target/riscv: update checks on writing pmpcfg for Smepmp to version 1.0

Alvin Chang posted 1 patch 7 months, 3 weeks ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20230915083047.4067186-1-alvinga@andestech.com
Maintainers: Palmer Dabbelt <palmer@dabbelt.com>, Alistair Francis <alistair.francis@wdc.com>, Bin Meng <bin.meng@windriver.com>, Weiwei Li <liweiwei@iscas.ac.cn>, Daniel Henrique Barboza <dbarboza@ventanamicro.com>, Liu Zhiwei <zhiwei_liu@linux.alibaba.com>
There is a newer version of this series
target/riscv/pmp.c | 40 ++++++++++++++++++++++++++++++++--------
1 file changed, 32 insertions(+), 8 deletions(-)
[PATCH v3] target/riscv: update checks on writing pmpcfg for Smepmp to version 1.0
Posted by Alvin Chang 7 months, 3 weeks ago 
Current checks on writing pmpcfg for Smepmp follows Smepmp version
0.9.1. However, Smepmp specification has already been ratified, and
there are some differences between version 0.9.1 and 1.0. In this
commit we update the checks of writing pmpcfg to follow Smepmp version
1.0.

When mseccfg.MML is set, the constraints to modify PMP rules are:
1. Locked rules cannot be removed or modified until a PMP reset, unless
   mseccfg.RLB is set.
2. From Smepmp specification version 1.0, chapter 2 section 4b:
   Adding a rule with executable privileges that either is M-mode-only
   or a locked Shared-Region is not possible and such pmpcfg writes are
   ignored, leaving pmpcfg unchanged.

The commit transfers the value of pmpcfg into the index of the Smepmp
truth table, and checks the rules by aforementioned specification
changes.

Signed-off-by: Alvin Chang <alvinga@andestech.com>
---
Changes from v2: Adopt switch case ranges and numerical order.

Changes from v1: Convert ePMP over to Smepmp.

 target/riscv/pmp.c | 40 ++++++++++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index a08cd95658..b144932b3b 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -99,16 +99,40 @@ static void pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
                 locked = false;
             }
 
-            /* mseccfg.MML is set */
-            if (MSECCFG_MML_ISSET(env)) {
-                /* not adding execute bit */
-                if ((val & PMP_LOCK) != 0 && (val & PMP_EXEC) != PMP_EXEC) {
+            /*
+             * mseccfg.MML is set. Locked rules cannot be removed or modified
+             * until a PMP reset. Besides, from Smepmp specification version 1.0
+             * , chapter 2 section 4b says:
+             * Adding a rule with executable privileges that either is
+             * M-mode-only or a locked Shared-Region is not possible and such
+             * pmpcfg writes are ignored, leaving pmpcfg unchanged.
+             */
+            if (MSECCFG_MML_ISSET(env) && !pmp_is_locked(env, pmp_index)) {
+                /*
+                 * Convert the PMP permissions to match the truth table in the
+                 * ePMP spec.
+                 */
+                const uint8_t epmp_operation =
+                    ((val & PMP_LOCK) >> 4) | ((val & PMP_READ) << 2) |
+                    (val & PMP_WRITE) | ((val & PMP_EXEC) >> 2);
+
+                switch (epmp_operation) {
+                case 0 ... 8:
                     locked = false;
-                }
-                /* shared region and not adding X bit */
-                if ((val & PMP_LOCK) != PMP_LOCK &&
-                    (val & 0x7) != (PMP_WRITE | PMP_EXEC)) {
+                    break;
+                case 9 ... 11:
+                    break;
+                case 12:
+                    locked = false;
+                    break;
+                case 13:
+                    break;
+                case 14:
+                case 15:
                     locked = false;
+                    break;
+                default:
+                    g_assert_not_reached();
                 }
             }
         } else {
-- 
2.34.1
Re: [PATCH v3] target/riscv: update checks on writing pmpcfg for Smepmp to version 1.0
Posted by Alistair Francis 7 months, 2 weeks ago 
On Fri, Sep 15, 2023 at 6:32 PM Alvin Chang <alvinga@andestech.com> wrote:
>
> Current checks on writing pmpcfg for Smepmp follows Smepmp version
> 0.9.1. However, Smepmp specification has already been ratified, and
> there are some differences between version 0.9.1 and 1.0. In this
> commit we update the checks of writing pmpcfg to follow Smepmp version
> 1.0.
>
> When mseccfg.MML is set, the constraints to modify PMP rules are:
> 1. Locked rules cannot be removed or modified until a PMP reset, unless
>    mseccfg.RLB is set.
> 2. From Smepmp specification version 1.0, chapter 2 section 4b:
>    Adding a rule with executable privileges that either is M-mode-only
>    or a locked Shared-Region is not possible and such pmpcfg writes are
>    ignored, leaving pmpcfg unchanged.
>
> The commit transfers the value of pmpcfg into the index of the Smepmp
> truth table, and checks the rules by aforementioned specification
> changes.
>
> Signed-off-by: Alvin Chang <alvinga@andestech.com>
> ---
> Changes from v2: Adopt switch case ranges and numerical order.
>
> Changes from v1: Convert ePMP over to Smepmp.

Did this part get lost?

Alistair

>
>  target/riscv/pmp.c | 40 ++++++++++++++++++++++++++++++++--------
>  1 file changed, 32 insertions(+), 8 deletions(-)
>
> diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
> index a08cd95658..b144932b3b 100644
> --- a/target/riscv/pmp.c
> +++ b/target/riscv/pmp.c
> @@ -99,16 +99,40 @@ static void pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
>                  locked = false;
>              }
>
> -            /* mseccfg.MML is set */
> -            if (MSECCFG_MML_ISSET(env)) {
> -                /* not adding execute bit */
> -                if ((val & PMP_LOCK) != 0 && (val & PMP_EXEC) != PMP_EXEC) {
> +            /*
> +             * mseccfg.MML is set. Locked rules cannot be removed or modified
> +             * until a PMP reset. Besides, from Smepmp specification version 1.0
> +             * , chapter 2 section 4b says:
> +             * Adding a rule with executable privileges that either is
> +             * M-mode-only or a locked Shared-Region is not possible and such
> +             * pmpcfg writes are ignored, leaving pmpcfg unchanged.
> +             */
> +            if (MSECCFG_MML_ISSET(env) && !pmp_is_locked(env, pmp_index)) {
> +                /*
> +                 * Convert the PMP permissions to match the truth table in the
> +                 * ePMP spec.
> +                 */
> +                const uint8_t epmp_operation =
> +                    ((val & PMP_LOCK) >> 4) | ((val & PMP_READ) << 2) |
> +                    (val & PMP_WRITE) | ((val & PMP_EXEC) >> 2);
> +
> +                switch (epmp_operation) {
> +                case 0 ... 8:
>                      locked = false;
> -                }
> -                /* shared region and not adding X bit */
> -                if ((val & PMP_LOCK) != PMP_LOCK &&
> -                    (val & 0x7) != (PMP_WRITE | PMP_EXEC)) {
> +                    break;
> +                case 9 ... 11:
> +                    break;
> +                case 12:
> +                    locked = false;
> +                    break;
> +                case 13:
> +                    break;
> +                case 14:
> +                case 15:
>                      locked = false;
> +                    break;
> +                default:
> +                    g_assert_not_reached();
>                  }
>              }
>          } else {
> --
> 2.34.1
>
>

Patchew 2.1-devel-0870f84

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