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[PATCH] target/riscv: Fix scountovf CSR behavior in VS-mode and M-mode

Jim Shu posted 1 patch 2 weeks, 5 days ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20260318024234.2772480-1-jim.shu@sifive.com
Maintainers: Palmer Dabbelt <palmer@dabbelt.com>, Alistair Francis <alistair.francis@wdc.com>, Weiwei Li <liwei1518@gmail.com>, Daniel Henrique Barboza <dbarboza@ventanamicro.com>, Liu Zhiwei <zhiwei_liu@linux.alibaba.com>
target/riscv/csr.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
[PATCH] target/riscv: Fix scountovf CSR behavior in VS-mode and M-mode
Posted by Jim Shu 2 weeks, 5 days ago 
From Sscofpmf spec [1]:
- In M-mode, scountovf bit X is always readable.
- in VS mode, scountovf bit X is readable when mcounteren bit X and
  hcounteren bit X are both set, and otherwise reads as zero.

[1] https://github.com/riscv/riscv-isa-manual/blob/main/src/sscofpmf.adoc

Signed-off-by: Jim Shu <jim.shu@sifive.com>
Signed-off-by: Max Chou <max.chou@sifive.com>
---
 target/riscv/csr.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 5064483917..a75281539b 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -1599,6 +1599,7 @@ static RISCVException read_scountovf(CPURISCVState *env, int csrno,
     int mhpmevt_start = CSR_MHPMEVENT3 - CSR_MCOUNTINHIBIT;
     int i;
     *val = 0;
+    bool virt = env->virt_enabled;
 
     /* Virtualize scountovf for counter delegation */
     if (riscv_cpu_cfg(env)->ext_sscofpmf &&
@@ -1609,8 +1610,19 @@ static RISCVException read_scountovf(CPURISCVState *env, int csrno,
     }
 
     for (i = mhpmevt_start; i < RV_MAX_MHPMEVENTS; i++) {
-        if ((get_field(env->mcounteren, BIT(i))) &&
-            (env->mhpmevent_val[i] & MHPMEVENT_BIT_OF)) {
+        if (env->priv < PRV_M) {
+            if (!get_field(env->mcounteren, BIT(i))) {
+                /* no mcounteren in S/HS-mode */
+                continue;
+            }
+
+            if (virt && !get_field(env->hcounteren, BIT(i))) {
+                /* no hcounteren in VS-mode */
+                continue;
+            }
+        }
+
+        if (env->mhpmevent_val[i] & MHPMEVENT_BIT_OF) {
             *val |= BIT(i);
         }
     }
-- 
2.43.0
Re: [PATCH] target/riscv: Fix scountovf CSR behavior in VS-mode and M-mode
Posted by Alistair Francis 2 weeks, 4 days ago 
On Wed, Mar 18, 2026 at 12:44 PM Jim Shu <jim.shu@sifive.com> wrote:
>
> From Sscofpmf spec [1]:
> - In M-mode, scountovf bit X is always readable.
> - in VS mode, scountovf bit X is readable when mcounteren bit X and
>   hcounteren bit X are both set, and otherwise reads as zero.
>
> [1] https://github.com/riscv/riscv-isa-manual/blob/main/src/sscofpmf.adoc
>
> Signed-off-by: Jim Shu <jim.shu@sifive.com>
> Signed-off-by: Max Chou <max.chou@sifive.com>

Thanks!

Applied to riscv-to-apply.next

Alistair

> ---
>  target/riscv/csr.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 5064483917..a75281539b 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -1599,6 +1599,7 @@ static RISCVException read_scountovf(CPURISCVState *env, int csrno,
>      int mhpmevt_start = CSR_MHPMEVENT3 - CSR_MCOUNTINHIBIT;
>      int i;
>      *val = 0;
> +    bool virt = env->virt_enabled;
>
>      /* Virtualize scountovf for counter delegation */
>      if (riscv_cpu_cfg(env)->ext_sscofpmf &&
> @@ -1609,8 +1610,19 @@ static RISCVException read_scountovf(CPURISCVState *env, int csrno,
>      }
>
>      for (i = mhpmevt_start; i < RV_MAX_MHPMEVENTS; i++) {
> -        if ((get_field(env->mcounteren, BIT(i))) &&
> -            (env->mhpmevent_val[i] & MHPMEVENT_BIT_OF)) {
> +        if (env->priv < PRV_M) {
> +            if (!get_field(env->mcounteren, BIT(i))) {
> +                /* no mcounteren in S/HS-mode */
> +                continue;
> +            }
> +
> +            if (virt && !get_field(env->hcounteren, BIT(i))) {
> +                /* no hcounteren in VS-mode */
> +                continue;
> +            }
> +        }
> +
> +        if (env->mhpmevent_val[i] & MHPMEVENT_BIT_OF) {
>              *val |= BIT(i);
>          }
>      }
> --
> 2.43.0
>
>
Re: [PATCH] target/riscv: Fix scountovf CSR behavior in VS-mode and M-mode
Posted by Alistair Francis 2 weeks, 4 days ago 
On Wed, Mar 18, 2026 at 12:44 PM Jim Shu <jim.shu@sifive.com> wrote:
>
> From Sscofpmf spec [1]:
> - In M-mode, scountovf bit X is always readable.
> - in VS mode, scountovf bit X is readable when mcounteren bit X and
>   hcounteren bit X are both set, and otherwise reads as zero.
>
> [1] https://github.com/riscv/riscv-isa-manual/blob/main/src/sscofpmf.adoc
>
> Signed-off-by: Jim Shu <jim.shu@sifive.com>
> Signed-off-by: Max Chou <max.chou@sifive.com>

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

Alistair

> ---
>  target/riscv/csr.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 5064483917..a75281539b 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -1599,6 +1599,7 @@ static RISCVException read_scountovf(CPURISCVState *env, int csrno,
>      int mhpmevt_start = CSR_MHPMEVENT3 - CSR_MCOUNTINHIBIT;
>      int i;
>      *val = 0;
> +    bool virt = env->virt_enabled;
>
>      /* Virtualize scountovf for counter delegation */
>      if (riscv_cpu_cfg(env)->ext_sscofpmf &&
> @@ -1609,8 +1610,19 @@ static RISCVException read_scountovf(CPURISCVState *env, int csrno,
>      }
>
>      for (i = mhpmevt_start; i < RV_MAX_MHPMEVENTS; i++) {
> -        if ((get_field(env->mcounteren, BIT(i))) &&
> -            (env->mhpmevent_val[i] & MHPMEVENT_BIT_OF)) {
> +        if (env->priv < PRV_M) {
> +            if (!get_field(env->mcounteren, BIT(i))) {
> +                /* no mcounteren in S/HS-mode */
> +                continue;
> +            }
> +
> +            if (virt && !get_field(env->hcounteren, BIT(i))) {
> +                /* no hcounteren in VS-mode */
> +                continue;
> +            }
> +        }
> +
> +        if (env->mhpmevent_val[i] & MHPMEVENT_BIT_OF) {
>              *val |= BIT(i);
>          }
>      }
> --
> 2.43.0
>
>

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