[PATCH v2 4/4] target/loongarch/kvm: fix cpucfg sync error handling

[Tao Cui <cui.tao@linux.dev>]

From: Tao Cui <cuitao@kylinos.cn>

In kvm_loongarch_get_cpucfg() and kvm_loongarch_put_cpucfg(), ret is
overwritten on each iteration, so only the last register's result is
returned and earlier failures are lost. On a failed read, env->cpucfg[i]
is stored from a stale or uninitialized val.

Accumulate errors with ret |=, matching kvm_loongarch_get_csr()/put_csr(),
and only update env->cpucfg[i] on a successful read. Keep the cpucfg2
negotiation check in put_cpucfg() on a separate variable so its early
return does not overwrite the accumulated result.

Signed-off-by: Tao Cui <cuitao@kylinos.cn>
---
 target/loongarch/kvm/kvm.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/target/loongarch/kvm/kvm.c b/target/loongarch/kvm/kvm.c
index a504cfaaf7..9f1ee41ef6 100644
--- a/target/loongarch/kvm/kvm.c
+++ b/target/loongarch/kvm/kvm.c
@@ -713,8 +713,11 @@ static int kvm_loongarch_get_cpucfg(CPUState *cs)
     CPULoongArchState *env = cpu_env(cs);
 
     for (i = 0; i < 21; i++) {
-        ret = kvm_get_one_reg(cs, KVM_IOC_CPUCFG(i), &val);
-        env->cpucfg[i] = (uint32_t)val;
+        int r = kvm_get_one_reg(cs, KVM_IOC_CPUCFG(i), &val);
+        ret |= r;
+        if (!r) {
+            env->cpucfg[i] = (uint32_t)val;
+        }
     }
     return ret;
 }
@@ -767,13 +770,13 @@ static int kvm_loongarch_put_cpucfg(CPUState *cs)
 
     for (i = 0; i < 21; i++) {
 	if (i == 2) {
-            ret = kvm_check_cpucfg2(cs);
-            if (ret) {
-                return ret;
+            int r = kvm_check_cpucfg2(cs);
+            if (r) {
+                return r;
             }
 	}
         val = env->cpucfg[i];
-        ret = kvm_set_one_reg(cs, KVM_IOC_CPUCFG(i), &val);
+        ret |= kvm_set_one_reg(cs, KVM_IOC_CPUCFG(i), &val);
     }
     return ret;
 }
-- 
2.43.0