target/loongarch: Set unused flag with CSR registers

On LA464, some CSR registers are not used such as CSR_SAVE8 -
CSR_SAVE15, also CSR registers relative with MCE is not used now.

Flag CSRFL_UNUSED is added for these registers, so that it will
not dumped. In order to keep compatiblity, these CSR registers are
not removed since it is used in vmstate already.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>

Author: bibo-mao

target/loongarch/cpu.c

@@ -19,7 +19,7 @@
 #include "cpu.h"
 #include "internals.h"
 #include "fpu/softfloat-helpers.h"
-#include "cpu-csr.h"
+#include "csr.h"
 #ifndef CONFIG_USER_ONLY
 #include "system/reset.h"
 #endif
@@ -375,6 +375,33 @@ static int loongarch_cpu_mmu_index(CPUState *cs, bool ifetch)
     return MMU_DA_IDX;
 }
 
+static void loongarch_la464_init_csr(Object *obj)
+{
+#ifndef CONFIG_USER_ONLY
+    static bool initialized;
+    LoongArchCPU *cpu = LOONGARCH_CPU(obj);
+    CPULoongArchState *env = &cpu->env;
+    int i, num;
+
+    if (!initialized) {
+        initialized = true;
+        num = FIELD_EX64(env->CSR_PRCFG1, CSR_PRCFG1, SAVE_NUM);
+        for (i = num; i < 16; i++) {
+            set_csr_flag(LOONGARCH_CSR_SAVE(i), CSRFL_UNUSED);
+        }
+        set_csr_flag(LOONGARCH_CSR_IMPCTL1, CSRFL_UNUSED);
+        set_csr_flag(LOONGARCH_CSR_IMPCTL2, CSRFL_UNUSED);
+        set_csr_flag(LOONGARCH_CSR_MERRCTL, CSRFL_UNUSED);
+        set_csr_flag(LOONGARCH_CSR_MERRINFO1, CSRFL_UNUSED);
+        set_csr_flag(LOONGARCH_CSR_MERRINFO2, CSRFL_UNUSED);
+        set_csr_flag(LOONGARCH_CSR_MERRENTRY, CSRFL_UNUSED);
+        set_csr_flag(LOONGARCH_CSR_MERRERA, CSRFL_UNUSED);
+        set_csr_flag(LOONGARCH_CSR_MERRSAVE, CSRFL_UNUSED);
+        set_csr_flag(LOONGARCH_CSR_CTAG, CSRFL_UNUSED);
+    }
+#endif
+}
+
 static void loongarch_la464_initfn(Object *obj)
 {
     LoongArchCPU *cpu = LOONGARCH_CPU(obj);
@@ -470,6 +497,7 @@ static void loongarch_la464_initfn(Object *obj)
     env->CSR_PRCFG3 = FIELD_DP64(env->CSR_PRCFG3, CSR_PRCFG3, STLB_WAYS, 7);
     env->CSR_PRCFG3 = FIELD_DP64(env->CSR_PRCFG3, CSR_PRCFG3, STLB_SETS, 8);
 
+    loongarch_la464_init_csr(obj);
     loongarch_cpu_post_init(obj);
 }
 

target/loongarch/csr.c

@@ -112,3 +112,16 @@ CSRInfo *get_csr(unsigned int csr_num)
 
     return csr;
 }
+
+bool set_csr_flag(unsigned int csr_num, int flag)
+{
+    CSRInfo *csr;
+
+    csr = get_csr(csr_num);
+    if (!csr) {
+        return false;
+    }
+
+    csr->flags |= flag;
+    return true;
+}

target/loongarch/csr.h

@@ -13,6 +13,7 @@ enum {
     CSRFL_READONLY = (1 << 0),
     CSRFL_EXITTB   = (1 << 1),
     CSRFL_IO       = (1 << 2),
+    CSRFL_UNUSED   = (1 << 3),
 };
 
 typedef struct {
@@ -23,4 +24,5 @@ typedef struct {
 } CSRInfo;
 
 CSRInfo *get_csr(unsigned int csr_num);
+bool set_csr_flag(unsigned int csr_num, int flag);
 #endif /* TARGET_LOONGARCH_CSR_H */