[PATCH v4] riscv/gdbstub: add V bit to priv reg

[Yanfeng Liu]

This adds virtualization mode (V bit) as bit(2) of register `priv`
per RiscV debug spec v1.0.0-rc4. Checked with gdb-multiarch v12.1.

Note that GDB may display `INVALID` tag for `priv` reg when V bit
is set, this doesn't affect actual access to the bit though.

Signed-off-by: Yanfeng Liu <yfliu2008@qq.com>
---
 target/riscv/gdbstub.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/target/riscv/gdbstub.c b/target/riscv/gdbstub.c
index c07df972f1..18e88f416a 100644
--- a/target/riscv/gdbstub.c
+++ b/target/riscv/gdbstub.c
@@ -213,7 +213,10 @@ static int riscv_gdb_get_virtual(CPUState *cs, GByteArray 
*buf, int n)
         RISCVCPU *cpu = RISCV_CPU(cs);
         CPURISCVState *env = &cpu->env;
 
-        return gdb_get_regl(buf, env->priv);
+        /* Per RiscV debug spec v1.0.0 rc4 */
+        target_ulong vbit = (env->virt_enabled) ? BIT(2) : 0;
+
+        return gdb_get_regl(buf, env->priv | vbit);
 #endif
     }
     return 0;
@@ -226,10 +229,22 @@ static int riscv_gdb_set_virtual(CPUState *cs, uint8_t 
*mem_buf, int n)
         RISCVCPU *cpu = RISCV_CPU(cs);
         CPURISCVState *env = &cpu->env;
 
-        env->priv = ldtul_p(mem_buf) & 0x3;
-        if (env->priv == PRV_RESERVED) {
-            env->priv = PRV_S;
+        target_ulong new_priv = ldtul_p(mem_buf) & 0x3;
+        bool new_virt = 0;
+
+        if (new_priv == PRV_RESERVED) {
+            new_priv = PRV_S;
+        }
+
+        if (new_priv != PRV_M) {
+            new_virt = (ldtul_p(mem_buf) & BIT(2)) >> 2;
         }
+
+        if (riscv_has_ext(env, RVH) && new_virt != env->virt_enabled) {
+            riscv_cpu_swap_hypervisor_regs(env);
+        }
+
+        riscv_cpu_set_mode(env, new_priv, new_virt);
 #endif
         return sizeof(target_ulong);
     }
-- 
2.34.1