i386: Add support for overflow recovery

Add cpuid bit definition for overflow recovery. This is needed in the case
where a deferred error has been sent to the guest, a guest process accesses the
poisoned memory, but the machine_check_poll function has not yet handled the
original deferred error. If overflow recovery is not set in this case, when we
handle the uncorrected error from the poisoned memory access, the overflow bit
will be set and will result in the guest being shut down.

By the time the MCE reaches the guest, the overflow has been handled
by the host and has not caused a shutdown, so include the bit unconditionally.

Signed-off-by: John Allen <john.allen@amd.com>
Message-ID: <20240603193622.47156-4-john.allen@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/cpu.c

@@ -1183,7 +1183,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
     [FEAT_8000_0007_EBX] = {
         .type = CPUID_FEATURE_WORD,
         .feat_names = {
-            NULL, "succor", NULL, NULL,
+            "overflow-recov", "succor", NULL, NULL,
             NULL, NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,

target/i386/cpu.h

@@ -984,6 +984,7 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
 #define CPUID_14_0_ECX_LIP              (1U << 31)
 
 /* RAS Features */
+#define CPUID_8000_0007_EBX_OVERFLOW_RECOV    (1U << 0)
 #define CPUID_8000_0007_EBX_SUCCOR      (1U << 1)
 
 /* CLZERO instruction */

target/i386/kvm/kvm.c

@@ -533,7 +533,7 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
         cpuid_1_edx = kvm_arch_get_supported_cpuid(s, 1, 0, R_EDX);
         ret |= cpuid_1_edx & CPUID_EXT2_AMD_ALIASES;
     } else if (function == 0x80000007 && reg == R_EBX) {
-        ret |= CPUID_8000_0007_EBX_SUCCOR;
+        ret |= CPUID_8000_0007_EBX_OVERFLOW_RECOV | CPUID_8000_0007_EBX_SUCCOR;
     } else if (function == KVM_CPUID_FEATURES && reg == R_EAX) {
         /* kvm_pv_unhalt is reported by GET_SUPPORTED_CPUID, but it can't
          * be enabled without the in-kernel irqchip