target/loongarch: Add compatible support about VM reboot

With edk2-stable202408 LoongArch UEFI bios, CSR PGD register is set only
if its value is equal to zero for boot cpu, it causes reboot issue. Since
CSR PGD register is changed with linux kernel, UEFI BIOS cannot use it.

Add workaround to clear CSR registers relative with TLB in function
loongarch_cpu_reset_hold(), so that VM can reboot with edk2-stable202408
UEFI bios.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20240827035807.3326293-1-maobibo@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>

target/loongarch/cpu.c

@@ -549,6 +549,20 @@ static void loongarch_cpu_reset_hold(Object *obj, ResetType type)
     env->CSR_TLBRERA = FIELD_DP64(env->CSR_TLBRERA, CSR_TLBRERA, ISTLBR, 0);
     env->CSR_MERRCTL = FIELD_DP64(env->CSR_MERRCTL, CSR_MERRCTL, ISMERR, 0);
     env->CSR_TID = cs->cpu_index;
+    /*
+     * Workaround for edk2-stable202408, CSR PGD register is set only if
+     * its value is equal to zero for boot cpu, it causes reboot issue.
+     *
+     * Here clear CSR registers relative with TLB.
+     */
+    env->CSR_PGDH = 0;
+    env->CSR_PGDL = 0;
+    env->CSR_PWCL = 0;
+    env->CSR_PWCH = 0;
+    env->CSR_STLBPS = 0;
+    env->CSR_EENTRY = 0;
+    env->CSR_TLBRENTRY = 0;
+    env->CSR_MERRENTRY = 0;
 
     for (n = 0; n < 4; n++) {
         env->CSR_DMW[n] = FIELD_DP64(env->CSR_DMW[n], CSR_DMW, PLV0, 0);