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 <[email protected]>
Reviewed-by: Chao Liu <[email protected]>
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
>
