The Zicfilp extension adds the MLPE field to the mseccfg CSR. According
to the RISC-V Privileged Specification, mseccfg exists if any extension
that adds a field to it is implemented.

Currently, the `have_mseccfg()` predicate function checks for Smepmp,
Zkr, and Smmpm, but misses Zicfilp. As a result, if a CPU is configured
with `zicfilp=true` but without the other extensions, accessing the
mseccfg CSR will incorrectly raise an illegal instruction exception.

This patch adds the missing check for `ext_zicfilp` to ensure the CSR
is properly accessible when the Zicfilp extension is enabled.

This issue was discovered and reported by SpecHunter, an AI-driven
architecture specification analysis tool.

Link: https://github.com/yizishun/rv-isa-sec/blob/master/output/riscv-isa-manual/pr-2561/qemu.txt
Signed-off-by: Zishun Yi <vulab@iscas.ac.cn>
---
v2: Removed mistakenly added #include "cpu_bits.h".
v3: add a missing space after the Link tag clon

 target/riscv/csr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index da366cf56271..e1cd4a299cb0 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -783,6 +783,9 @@ static RISCVException have_mseccfg(CPURISCVState *env, int csrno)
     if (riscv_cpu_cfg(env)->ext_smmpm) {
         return RISCV_EXCP_NONE;
     }
+    if (riscv_cpu_cfg(env)->ext_zicfilp) {
+        return RISCV_EXCP_NONE;
+    }
 
     return RISCV_EXCP_ILLEGAL_INST;
 }
-- 
2.51.2

On Mon, May 11, 2026 at 7:56 PM Zishun Yi <vulab@iscas.ac.cn> wrote:
>
> The Zicfilp extension adds the MLPE field to the mseccfg CSR. According
> to the RISC-V Privileged Specification, mseccfg exists if any extension
> that adds a field to it is implemented.
>
> Currently, the `have_mseccfg()` predicate function checks for Smepmp,
> Zkr, and Smmpm, but misses Zicfilp. As a result, if a CPU is configured
> with `zicfilp=true` but without the other extensions, accessing the
> mseccfg CSR will incorrectly raise an illegal instruction exception.
>
> This patch adds the missing check for `ext_zicfilp` to ensure the CSR
> is properly accessible when the Zicfilp extension is enabled.
>
> This issue was discovered and reported by SpecHunter, an AI-driven
> architecture specification analysis tool.
>
> Link: https://github.com/yizishun/rv-isa-sec/blob/master/output/riscv-isa-manual/pr-2561/qemu.txt
> Signed-off-by: Zishun Yi <vulab@iscas.ac.cn>

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

Alistair

> ---
> v2: Removed mistakenly added #include "cpu_bits.h".
> v3: add a missing space after the Link tag clon
>
>  target/riscv/csr.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index da366cf56271..e1cd4a299cb0 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -783,6 +783,9 @@ static RISCVException have_mseccfg(CPURISCVState *env, int csrno)
>      if (riscv_cpu_cfg(env)->ext_smmpm) {
>          return RISCV_EXCP_NONE;
>      }
> +    if (riscv_cpu_cfg(env)->ext_zicfilp) {
> +        return RISCV_EXCP_NONE;
> +    }
>
>      return RISCV_EXCP_ILLEGAL_INST;
>  }
> --
> 2.51.2
>
>

On Mon, May 11, 2026 at 03:27:05PM +0800, Zishun Yi wrote:
> The Zicfilp extension adds the MLPE field to the mseccfg CSR. According
> to the RISC-V Privileged Specification, mseccfg exists if any extension
> that adds a field to it is implemented.
> 
> Currently, the `have_mseccfg()` predicate function checks for Smepmp,
> Zkr, and Smmpm, but misses Zicfilp. As a result, if a CPU is configured
> with `zicfilp=true` but without the other extensions, accessing the
> mseccfg CSR will incorrectly raise an illegal instruction exception.
> 
> This patch adds the missing check for `ext_zicfilp` to ensure the CSR
> is properly accessible when the Zicfilp extension is enabled.
> 
> This issue was discovered and reported by SpecHunter, an AI-driven
> architecture specification analysis tool.
> 
> Link: https://github.com/yizishun/rv-isa-sec/blob/master/output/riscv-isa-manual/pr-2561/qemu.txt
> Signed-off-by: Zishun Yi <vulab@iscas.ac.cn>
Reviewed-by: Chao Liu <chao.liu.zevorn@gmail.com>

Thanks,
Chao
> ---
> v2: Removed mistakenly added #include "cpu_bits.h".
> v3: add a missing space after the Link tag clon
> 
>  target/riscv/csr.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index da366cf56271..e1cd4a299cb0 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -783,6 +783,9 @@ static RISCVException have_mseccfg(CPURISCVState *env, int csrno)
>      if (riscv_cpu_cfg(env)->ext_smmpm) {
>          return RISCV_EXCP_NONE;
>      }
> +    if (riscv_cpu_cfg(env)->ext_zicfilp) {
> +        return RISCV_EXCP_NONE;
> +    }
>  
>      return RISCV_EXCP_ILLEGAL_INST;
>  }
> -- 
> 2.51.2
>

On 5/11/2026 4:27 AM, Zishun Yi wrote:
> The Zicfilp extension adds the MLPE field to the mseccfg CSR. According
> to the RISC-V Privileged Specification, mseccfg exists if any extension
> that adds a field to it is implemented.
> 
> Currently, the `have_mseccfg()` predicate function checks for Smepmp,
> Zkr, and Smmpm, but misses Zicfilp. As a result, if a CPU is configured
> with `zicfilp=true` but without the other extensions, accessing the
> mseccfg CSR will incorrectly raise an illegal instruction exception.
> 
> This patch adds the missing check for `ext_zicfilp` to ensure the CSR
> is properly accessible when the Zicfilp extension is enabled.
> 
> This issue was discovered and reported by SpecHunter, an AI-driven
> architecture specification analysis tool.
> 
> Link: https://github.com/yizishun/rv-isa-sec/blob/master/output/riscv-isa-manual/pr-2561/qemu.txt
> Signed-off-by: Zishun Yi <vulab@iscas.ac.cn>
> ---

Reviewed-by: Daniel Henrique Barboza <daniel.barboza@oss.qualcomm.com>

> v2: Removed mistakenly added #include "cpu_bits.h".
> v3: add a missing space after the Link tag clon
> 
>   target/riscv/csr.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index da366cf56271..e1cd4a299cb0 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -783,6 +783,9 @@ static RISCVException have_mseccfg(CPURISCVState *env, int csrno)
>       if (riscv_cpu_cfg(env)->ext_smmpm) {
>           return RISCV_EXCP_NONE;
>       }
> +    if (riscv_cpu_cfg(env)->ext_zicfilp) {
> +        return RISCV_EXCP_NONE;
> +    }
>   
>       return RISCV_EXCP_ILLEGAL_INST;
>   }