target/riscv/kvm: fix shadowing in kvm_riscv_(get|put)_regs_csr

KVM_RISCV_GET_CSR() and KVM_RISCV_SET_CSR() use an 'int ret' variable
that is used to do an early 'return' if ret > 0. Both are being called
in functions that are also declaring a 'ret' integer, initialized with
'0', and this integer is used as return of the function.

The result is that the compiler is less than pleased and is pointing
shadowing errors:

../target/riscv/kvm/kvm-cpu.c: In function 'kvm_riscv_get_regs_csr':
../target/riscv/kvm/kvm-cpu.c:90:13: error: declaration of 'ret' shadows a previous local [-Werror=shadow=compatible-local]
   90 |         int ret = kvm_get_one_reg(cs, RISCV_CSR_REG(env, csr), &reg); \
      |             ^~~
../target/riscv/kvm/kvm-cpu.c:539:5: note: in expansion of macro 'KVM_RISCV_GET_CSR'
  539 |     KVM_RISCV_GET_CSR(cs, env, sstatus, env->mstatus);
      |     ^~~~~~~~~~~~~~~~~
../target/riscv/kvm/kvm-cpu.c:536:9: note: shadowed declaration is here
  536 |     int ret = 0;
      |         ^~~

../target/riscv/kvm/kvm-cpu.c: In function 'kvm_riscv_put_regs_csr':
../target/riscv/kvm/kvm-cpu.c:98:13: error: declaration of 'ret' shadows a previous local [-Werror=shadow=compatible-local]
   98 |         int ret = kvm_set_one_reg(cs, RISCV_CSR_REG(env, csr), &reg); \
      |             ^~~
../target/riscv/kvm/kvm-cpu.c:556:5: note: in expansion of macro 'KVM_RISCV_SET_CSR'
  556 |     KVM_RISCV_SET_CSR(cs, env, sstatus, env->mstatus);
      |     ^~~~~~~~~~~~~~~~~
../target/riscv/kvm/kvm-cpu.c:553:9: note: shadowed declaration is here
  553 |     int ret = 0;
      |         ^~~

The macros are doing early returns for non-zero returns and the local
'ret' variable for both functions is used just to do 'return 0', so
remove them from kvm_riscv_get_regs_csr() and kvm_riscv_put_regs_csr()
and do a straight 'return 0' in the end.

For good measure let's also rename the 'ret' variables in
KVM_RISCV_GET_CSR() and KVM_RISCV_SET_CSR() to '_ret' to make them more
resilient to these kind of errors.

Fixes: 937f0b4512 ("target/riscv: Implement kvm_arch_get_registers")
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20231123101338.1040134-1-dbarboza@ventanamicro.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

target/riscv/kvm/kvm-cpu.c

@@ -87,17 +87,17 @@ static uint64_t kvm_riscv_reg_id(CPURISCVState *env, uint64_t type,
 
 #define KVM_RISCV_GET_CSR(cs, env, csr, reg) \
     do { \
-        int ret = kvm_get_one_reg(cs, RISCV_CSR_REG(env, csr), &reg); \
-        if (ret) { \
-            return ret; \
+        int _ret = kvm_get_one_reg(cs, RISCV_CSR_REG(env, csr), &reg); \
+        if (_ret) { \
+            return _ret; \
         } \
     } while (0)
 
 #define KVM_RISCV_SET_CSR(cs, env, csr, reg) \
     do { \
-        int ret = kvm_set_one_reg(cs, RISCV_CSR_REG(env, csr), &reg); \
-        if (ret) { \
-            return ret; \
+        int _ret = kvm_set_one_reg(cs, RISCV_CSR_REG(env, csr), &reg); \
+        if (_ret) { \
+            return _ret; \
         } \
     } while (0)
 
@@ -533,7 +533,6 @@ static int kvm_riscv_put_regs_core(CPUState *cs)
 
 static int kvm_riscv_get_regs_csr(CPUState *cs)
 {
-    int ret = 0;
     CPURISCVState *env = &RISCV_CPU(cs)->env;
 
     KVM_RISCV_GET_CSR(cs, env, sstatus, env->mstatus);
@@ -545,12 +544,12 @@ static int kvm_riscv_get_regs_csr(CPUState *cs)
     KVM_RISCV_GET_CSR(cs, env, stval, env->stval);
     KVM_RISCV_GET_CSR(cs, env, sip, env->mip);
     KVM_RISCV_GET_CSR(cs, env, satp, env->satp);
-    return ret;
+
+    return 0;
 }
 
 static int kvm_riscv_put_regs_csr(CPUState *cs)
 {
-    int ret = 0;
     CPURISCVState *env = &RISCV_CPU(cs)->env;
 
     KVM_RISCV_SET_CSR(cs, env, sstatus, env->mstatus);
@@ -563,7 +562,7 @@ static int kvm_riscv_put_regs_csr(CPUState *cs)
     KVM_RISCV_SET_CSR(cs, env, sip, env->mip);
     KVM_RISCV_SET_CSR(cs, env, satp, env->satp);
 
-    return ret;
+    return 0;
 }
 
 static int kvm_riscv_get_regs_fp(CPUState *cs)