[PATCH 1/2] target/riscv: Lower bound of VLEN is 32, and check VLEN >= ELEN

[Kito Cheng]

According RVV spec 1.0, the minmal requirement of VLEN is great than or
equal to ELEN, and minmal possible ELEN is 32, and also spec has mention
`Minimum VLEN` for zve32* is 32, so the lower bound of VLEN is 32 I
think.

[1] 
https://github.com/riscv/riscv-v-spec/blob/master/v-spec.adoc#2-implementation-defined-constant-parameters
[2] 
https://github.com/riscv/riscv-v-spec/blob/master/v-spec.adoc#182-zve-vector-extensions-for-embedded-processors

Signed-off-by: Kito Cheng <kito.cheng@sifive.com>
---
 target/riscv/cpu.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 1bb3973806..487d0faa63 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -740,10 +740,10 @@ static void riscv_cpu_realize(DeviceState *dev, Error 
**errp)
                         "Vector extension VLEN must be power of 2");
                 return;
             }
-            if (cpu->cfg.vlen > RV_VLEN_MAX || cpu->cfg.vlen < 128) {
+            if (cpu->cfg.vlen > RV_VLEN_MAX || cpu->cfg.vlen < 32) {
                 error_setg(errp,
                         "Vector extension implementation only supports VLEN "
-                        "in the range [128, %d]", RV_VLEN_MAX);
+                        "in the range [32, %d]", RV_VLEN_MAX);
                 return;
             }
             if (!is_power_of_2(cpu->cfg.elen)) {
@@ -757,6 +757,12 @@ static void riscv_cpu_realize(DeviceState *dev, Error 
**errp)
                         "in the range [8, 64]");
                 return;
             }
+            if (cpu->cfg.vlen < cpu->cfg.elen) {
+                error_setg(errp,
+                        "Vector extension VLEN must be greater than or equal "
+                        "to ELEN");
+                return;
+            }
             if (cpu->cfg.vext_spec) {
                 if (!g_strcmp0(cpu->cfg.vext_spec, "v1.0")) {
                     vext_version = VEXT_VERSION_1_00_0;
-- 
2.34.0