target/riscv: rvv: Modify minimum VLEN according to enabled vector extensions

According to the RISC-V unprivileged specification, the VLEN should be greater
or equal to the ELEN. This commit modifies the minimum VLEN based on the vector
extensions and introduces a check rule for VLEN and ELEN.

  Extension     Minimum VLEN
* V                      128
* Zve64[d|f|x]            64
* Zve32[f|x]              32

Signed-off-by: Max Chou <max.chou@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250923090729.1887406-3-max.chou@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

1 files changed, 17 insertions, 2 deletions

diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index b3b7f14503..1150bd1469 100644
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -417,12 +417,21 @@ static void riscv_cpu_validate_misa_priv(CPURISCVState *env, Error **errp)
 static void riscv_cpu_validate_v(CPURISCVState *env, RISCVCPUConfig *cfg,
                                  Error **errp)
 {
+    uint32_t min_vlen;
     uint32_t vlen = cfg->vlenb << 3;
 
-    if (vlen > RV_VLEN_MAX || vlen < 128) {
+    if (riscv_has_ext(env, RVV)) {
+        min_vlen = 128;
+    } else if (cfg->ext_zve64x) {
+        min_vlen = 64;
+    } else if (cfg->ext_zve32x) {
+        min_vlen = 32;
+    }
+
+    if (vlen > RV_VLEN_MAX || vlen < min_vlen) {
         error_setg(errp,
                    "Vector extension implementation only supports VLEN "
-                   "in the range [128, %d]", RV_VLEN_MAX);
+                   "in the range [%d, %d]", min_vlen, RV_VLEN_MAX);
         return;
     }
 
@@ -432,6 +441,12 @@ static void riscv_cpu_validate_v(CPURISCVState *env, RISCVCPUConfig *cfg,
                    "in the range [8, 64]");
         return;
     }
+
+    if (vlen < cfg->elen) {
+        error_setg(errp, "Vector extension implementation requires VLEN "
+                         "to be greater than or equal to ELEN");
+        return;
+    }
 }
 
 static void riscv_cpu_disable_priv_spec_isa_exts(RISCVCPU *cpu)