i386: do kvm_put_msr_feature_control() first thing when vCPU is reset

kvm_put_sregs2() fails to reset 'locked' CR4/CR0 bits upon vCPU reset when
it is in VMX root operation. Do kvm_put_msr_feature_control() before
kvm_put_sregs2() to (possibly) kick vCPU out of VMX root operation. It also
seems logical to do kvm_put_msr_feature_control() before
kvm_put_nested_state() and not after it, especially when 'real' nested
state is set.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220818150113.479917-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 4f8dacc1d4b51ee69358d902530f4fb2cd5d0d80..a1fd1f53791df96bfab30e6764956a6fe02ee471 100644 (file)
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -4529,6 +4529,18 @@ int kvm_arch_put_registers(CPUState *cpu, int level)
 
     assert(cpu_is_stopped(cpu) || qemu_cpu_is_self(cpu));
 
+    /*
+     * Put MSR_IA32_FEATURE_CONTROL first, this ensures the VM gets out of VMX
+     * root operation upon vCPU reset. kvm_put_msr_feature_control() should also
+     * preceed kvm_put_nested_state() when 'real' nested state is set.
+     */
+    if (level >= KVM_PUT_RESET_STATE) {
+        ret = kvm_put_msr_feature_control(x86_cpu);
+        if (ret < 0) {
+            return ret;
+        }
+    }
+
     /* must be before kvm_put_nested_state so that EFER.SVME is set */
     ret = has_sregs2 ? kvm_put_sregs2(x86_cpu) : kvm_put_sregs(x86_cpu);
     if (ret < 0) {
@@ -4540,11 +4552,6 @@ int kvm_arch_put_registers(CPUState *cpu, int level)
         if (ret < 0) {
             return ret;
         }
-
-        ret = kvm_put_msr_feature_control(x86_cpu);
-        if (ret < 0) {
-            return ret;
-        }
     }
 
     if (level == KVM_PUT_FULL_STATE) {