[PATCH RFC v1 1/2] i386: reset KVM nested state upon CPU reset

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Make sure env->nested_state is cleaned up when a vCPU is reset, it may
be stale after an incoming migration, kvm_arch_put_registers() may
end up failing or putting vCPU in a weird state.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 target/i386/kvm/kvm.c | 37 +++++++++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index f148a6d52fa4..4f8dacc1d4b5 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1695,6 +1695,30 @@ static void kvm_init_xsave(CPUX86State *env)
            env->xsave_buf_len);
 }
 
+static void kvm_init_nested_state(CPUX86State *env)
+{
+    struct kvm_vmx_nested_state_hdr *vmx_hdr;
+    uint32_t size;
+
+    if (!env->nested_state) {
+        return;
+    }
+
+    size = env->nested_state->size;
+
+    memset(env->nested_state, 0, size);
+    env->nested_state->size = size;
+
+    if (cpu_has_vmx(env)) {
+        env->nested_state->format = KVM_STATE_NESTED_FORMAT_VMX;
+        vmx_hdr = &env->nested_state->hdr.vmx;
+        vmx_hdr->vmxon_pa = -1ull;
+        vmx_hdr->vmcs12_pa = -1ull;
+    } else if (cpu_has_svm(env)) {
+        env->nested_state->format = KVM_STATE_NESTED_FORMAT_SVM;
+    }
+}
+
 int kvm_arch_init_vcpu(CPUState *cs)
 {
     struct {
@@ -2122,19 +2146,10 @@ int kvm_arch_init_vcpu(CPUState *cs)
         assert(max_nested_state_len >= offsetof(struct kvm_nested_state, data));
 
         if (cpu_has_vmx(env) || cpu_has_svm(env)) {
-            struct kvm_vmx_nested_state_hdr *vmx_hdr;
-
             env->nested_state = g_malloc0(max_nested_state_len);
             env->nested_state->size = max_nested_state_len;
 
-            if (cpu_has_vmx(env)) {
-                env->nested_state->format = KVM_STATE_NESTED_FORMAT_VMX;
-                vmx_hdr = &env->nested_state->hdr.vmx;
-                vmx_hdr->vmxon_pa = -1ull;
-                vmx_hdr->vmcs12_pa = -1ull;
-            } else {
-                env->nested_state->format = KVM_STATE_NESTED_FORMAT_SVM;
-            }
+            kvm_init_nested_state(env);
         }
     }
 
@@ -2199,6 +2214,8 @@ void kvm_arch_reset_vcpu(X86CPU *cpu)
     /* enabled by default */
     env->poll_control_msr = 1;
 
+    kvm_init_nested_state(env);
+
     sev_es_set_reset_vector(CPU(cpu));
 }
 
-- 
2.37.1