From 8664cd20e4cdb8594076a26dacef592a4b4816b2 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 20 Jan 2020 19:21:44 +0100
Subject: [PATCH] target/i386: kvm: initialize microcode revision from KVM

KVM can return the host microcode revision as a feature MSR.
Use it as the default value for -cpu host.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1579544504-3616-4-git-send-email-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 target/i386/cpu.c | 4 ++++
 target/i386/kvm.c | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index ec8bc9957e..1962f00c77 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6330,6 +6330,10 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
                        &cpu->mwait.ecx, &cpu->mwait.edx);
             env->features[FEAT_1_ECX] |= CPUID_EXT_MONITOR;
         }
+        if (kvm_enabled() && cpu->ucode_rev == 0) {
+            cpu->ucode_rev = kvm_arch_get_supported_msr_feature(kvm_state,
+                                                                MSR_IA32_UCODE_REV);
+        }
     }
 
     if (cpu->ucode_rev == 0) {
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 60060087fd..7437f86130 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -2628,6 +2628,11 @@ static void kvm_init_msrs(X86CPU *cpu)
                           env->features[FEAT_CORE_CAPABILITY]);
     }
 
+    if (kvm_arch_get_supported_msr_feature(kvm_state,
+                                           MSR_IA32_UCODE_REV)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_UCODE_REV, cpu->ucode_rev);
+    }
+
     /*
      * Older kernels do not include VMX MSRs in KVM_GET_MSR_INDEX_LIST, but
      * all kernels with MSR features should have them.
-- 
2.27.0