diff --git a/target-xtensa/core-dc232b.c b/target-xtensa/core-dc232b.c
index a3b914bad4a77092c6712b0c6a0e18081920cee0..06826c042f2994e6569fade4e186d0bf55f3d6a4 100644
--- a/target-xtensa/core-dc232b.c
+++ b/target-xtensa/core-dc232b.c
@@ -33,7 +33,7 @@
 #include "core-dc232b/core-isa.h"
 #include "overlay_tool.h"
 
-static const XtensaConfig dc232b __attribute__((unused)) = {
+static XtensaConfig dc232b __attribute__((unused)) = {
     .name = "dc232b",
     .gdb_regmap = {
         .num_regs = 120,
diff --git a/target-xtensa/core-dc233c.c b/target-xtensa/core-dc233c.c
index ac745d106ff3ae76757acdb958f9cbbea3b77bbf..8daf7d9f8498c911833df43db3fe116913cf981b 100644
--- a/target-xtensa/core-dc233c.c
+++ b/target-xtensa/core-dc233c.c
@@ -34,7 +34,7 @@
 #include "core-dc233c/core-isa.h"
 #include "overlay_tool.h"
 
-static const XtensaConfig dc233c __attribute__((unused)) = {
+static XtensaConfig dc233c __attribute__((unused)) = {
     .name = "dc233c",
     .gdb_regmap = {
         .num_regs = 121,
diff --git a/target-xtensa/core-fsf.c b/target-xtensa/core-fsf.c
index cfcc840255ee850e347695426152b6c4e3099d6f..f6ea6b944a404733b91af84dc4be3062d11df861 100644
--- a/target-xtensa/core-fsf.c
+++ b/target-xtensa/core-fsf.c
@@ -33,9 +33,14 @@
 #include "core-fsf/core-isa.h"
 #include "overlay_tool.h"
 
-static const XtensaConfig fsf __attribute__((unused)) = {
+static XtensaConfig fsf __attribute__((unused)) = {
     .name = "fsf",
+    .gdb_regmap = {
     /* GDB for this core is not supported currently */
+        .reg = {
+            XTREG_END
+        },
+    },
     .clock_freq_khz = 10000,
     DEFAULT_SECTIONS
 };
diff --git a/target-xtensa/cpu.h b/target-xtensa/cpu.h
index dfd0d1ceda5a1db1e7eb78377f16519b7c514aea..b89c60245de7c6cc94023a93bc5ff878eb32c455 100644
--- a/target-xtensa/cpu.h
+++ b/target-xtensa/cpu.h
@@ -287,6 +287,7 @@ typedef struct XtensaGdbReg {
     int targno;
     int type;
     int group;
+    unsigned size;
 } XtensaGdbReg;
 
 typedef struct XtensaGdbRegmap {
@@ -336,6 +337,18 @@ typedef struct XtensaConfigList {
     struct XtensaConfigList *next;
 } XtensaConfigList;
 
+#ifdef HOST_WORDS_BIGENDIAN
+enum {
+    FP_F32_HIGH,
+    FP_F32_LOW,
+};
+#else
+enum {
+    FP_F32_LOW,
+    FP_F32_HIGH,
+};
+#endif
+
 typedef struct CPUXtensaState {
     const XtensaConfig *config;
     uint32_t regs[16];
@@ -343,7 +356,10 @@ typedef struct CPUXtensaState {
     uint32_t sregs[256];
     uint32_t uregs[256];
     uint32_t phys_regs[MAX_NAREG];
-    float32 fregs[16];
+    union {
+        float32 f32[2];
+        float64 f64;
+    } fregs[16];
     float_status fp_status;
 
     xtensa_tlb_entry itlb[7][MAX_TLB_WAY_SIZE];
@@ -384,6 +400,7 @@ XtensaCPU *cpu_xtensa_init(const char *cpu_model);
 void xtensa_translate_init(void);
 void xtensa_breakpoint_handler(CPUState *cs);
 int cpu_xtensa_exec(CPUXtensaState *s);
+void xtensa_finalize_config(XtensaConfig *config);
 void xtensa_register_core(XtensaConfigList *node);
 void check_interrupts(CPUXtensaState *s);
 void xtensa_irq_init(CPUXtensaState *env);
diff --git a/target-xtensa/gdbstub.c b/target-xtensa/gdbstub.c
index 9e13b20c4615a2b2a25086e67c7c577df8510326..bc2e1b55f67d6c1e81936c51a820c2773980c874 100644
--- a/target-xtensa/gdbstub.c
+++ b/target-xtensa/gdbstub.c
@@ -26,6 +26,7 @@ int xtensa_cpu_gdb_read_register(CPUState *cs, uint8_t *mem_buf, int n)
     XtensaCPU *cpu = XTENSA_CPU(cs);
     CPUXtensaState *env = &cpu->env;
     const XtensaGdbReg *reg = env->config->gdb_regmap.reg + n;
+    unsigned i;
 
     if (n < 0 || n >= env->config->gdb_regmap.num_regs) {
         return 0;
@@ -47,8 +48,16 @@ int xtensa_cpu_gdb_read_register(CPUState *cs, uint8_t *mem_buf, int n)
         return gdb_get_reg32(mem_buf, env->uregs[reg->targno & 0xff]);
 
     case 4: /*f*/
-        return gdb_get_reg32(mem_buf, float32_val(env->fregs[reg->targno
-                                                             & 0x0f]));
+        i = reg->targno & 0x0f;
+        switch (reg->size) {
+        case 4:
+            return gdb_get_reg32(mem_buf,
+                                 float32_val(env->fregs[i].f32[FP_F32_LOW]));
+        case 8:
+            return gdb_get_reg64(mem_buf, float64_val(env->fregs[i].f64));
+        default:
+            return 0;
+        }
 
     case 8: /*a*/
         return gdb_get_reg32(mem_buf, env->regs[reg->targno & 0x0f]);
@@ -92,8 +101,16 @@ int xtensa_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
         break;
 
     case 4: /*f*/
-        env->fregs[reg->targno & 0x0f] = make_float32(tmp);
-        break;
+        switch (reg->size) {
+        case 4:
+            env->fregs[reg->targno & 0x0f].f32[FP_F32_LOW] = make_float32(tmp);
+            return 4;
+        case 8:
+            env->fregs[reg->targno & 0x0f].f64 = make_float64(tmp);
+            return 8;
+        default:
+            return 0;
+        }
 
     case 8: /*a*/
         env->regs[reg->targno & 0x0f] = tmp;
diff --git a/target-xtensa/helper.c b/target-xtensa/helper.c
index d84d259cf890b27e53b7b0b386f35962b3841407..76be50d09c025c50e975cdbeded521f9f64c1f8c 100644
--- a/target-xtensa/helper.c
+++ b/target-xtensa/helper.c
@@ -51,6 +51,20 @@ static void xtensa_core_class_init(ObjectClass *oc, void *data)
     cc->gdb_num_core_regs = config->gdb_regmap.num_regs;
 }
 
+void xtensa_finalize_config(XtensaConfig *config)
+{
+    unsigned i, n = 0;
+
+    if (config->gdb_regmap.num_regs) {
+        return;
+    }
+
+    for (i = 0; config->gdb_regmap.reg[i].targno >= 0; ++i) {
+        n += (config->gdb_regmap.reg[i].type != 6);
+    }
+    config->gdb_regmap.num_regs = n;
+}
+
 void xtensa_register_core(XtensaConfigList *node)
 {
     TypeInfo type = {
diff --git a/target-xtensa/import_core.sh b/target-xtensa/import_core.sh
index 73791ec545511254aaa1d1a62a358ac93ca43783..351bee41c2d2fd6ac9a6ded42ea0d79b0ff995b2 100755
--- a/target-xtensa/import_core.sh
+++ b/target-xtensa/import_core.sh
@@ -22,8 +22,7 @@ mkdir -p "$TARGET"
 tar -xf "$OVERLAY" -C "$TARGET" --strip-components=1 \
     --xform='s/core/core-isa/' config/core.h
 tar -xf "$OVERLAY" -O gdb/xtensa-config.c | \
-    sed -n '1,/*\//p;/pc/,/a15/p' > "$TARGET"/gdb-config.c
-NUM_REGS=$(grep XTREG "$TARGET"/gdb-config.c | wc -l)
+    sed -n '1,/*\//p;/XTREG/,/XTREG_END/p' > "$TARGET"/gdb-config.c
 
 cat <<EOF > "${TARGET}.c"
 #include "cpu.h"
@@ -34,10 +33,9 @@ cat <<EOF > "${TARGET}.c"
 #include "core-$NAME/core-isa.h"
 #include "overlay_tool.h"
 
-static const XtensaConfig $NAME __attribute__((unused)) = {
+static XtensaConfig $NAME __attribute__((unused)) = {
     .name = "$NAME",
     .gdb_regmap = {
-        .num_regs = $NUM_REGS,
         .reg = {
 #include "core-$NAME/gdb-config.c"
         }
diff --git a/target-xtensa/overlay_tool.h b/target-xtensa/overlay_tool.h
index 6105d4c8ffbe2e6bfc3ba0e931b8d22797bbe97e..eda03aaca93b25b2f35147ed00ab7df75dcbba87 100644
--- a/target-xtensa/overlay_tool.h
+++ b/target-xtensa/overlay_tool.h
@@ -27,7 +27,8 @@
 
 #define XTREG(idx, ofs, bi, sz, al, no, flags, cp, typ, grp, name, \
         a1, a2, a3, a4, a5, a6) \
-    { .targno = (no), .type = (typ), .group = (grp) },
+    { .targno = (no), .type = (typ), .group = (grp), .size = (sz) },
+#define XTREG_END { .targno = -1 },
 
 #ifndef XCHAL_HAVE_DIV32
 #define XCHAL_HAVE_DIV32 0
@@ -316,6 +317,7 @@
         static XtensaConfigList node = { \
             .config = &core, \
         }; \
+        xtensa_finalize_config(&core); \
         xtensa_register_core(&node); \
     }
 #else
diff --git a/target-xtensa/translate.c b/target-xtensa/translate.c
index 86e4849fb652cc9bf8c6d909c37053d9a93f7b2b..f2118c24c03522b09c3a442376ef9257ec1f1e2f 100644
--- a/target-xtensa/translate.c
+++ b/target-xtensa/translate.c
@@ -228,7 +228,7 @@ void xtensa_translate_init(void)
 
     for (i = 0; i < 16; i++) {
         cpu_FR[i] = tcg_global_mem_new_i32(TCG_AREG0,
-                offsetof(CPUXtensaState, fregs[i]),
+                offsetof(CPUXtensaState, fregs[i].f32[FP_F32_LOW]),
                 fregnames[i]);
     }
 
@@ -3206,8 +3206,9 @@ void xtensa_cpu_dump_state(CPUState *cs, FILE *f,
 
         for (i = 0; i < 16; ++i) {
             cpu_fprintf(f, "F%02d=%08x (%+10.8e)%c", i,
-                    float32_val(env->fregs[i]),
-                    *(float *)&env->fregs[i], (i % 2) == 1 ? '\n' : ' ');
+                    float32_val(env->fregs[i].f32[FP_F32_LOW]),
+                    *(float *)(env->fregs[i].f32 + FP_F32_LOW),
+                    (i % 2) == 1 ? '\n' : ' ');
         }
     }
 }