KVM: add support for AMD nested live migration

Support for nested guest live migration is part of Linux 5.8, add the
corresponding code to QEMU.  The migration format consists of a few
flags, is an opaque 4k blob.

The blob is in VMCB format (the control area represents the L1 VMCB
control fields, the save area represents the pre-vmentry state; KVM does
not use the host save area since the AMD manual allows that) but QEMU
does not really care about that.  However, the flags need to be
copied to hflags/hflags2 and back.

In addition, support for retrieving and setting the AMD nested virtualization
states allows the L1 guest to be reset while running a nested guest, but
a small bug in CPU reset needs to be fixed for that to work.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 30 insertions, 1 deletions

diff --git a/target/i386/machine.c b/target/i386/machine.c
index 0c96531..b1acf7d 100644
--- a/target/i386/machine.c
+++ b/target/i386/machine.c
@@ -1071,13 +1071,41 @@ static const VMStateDescription vmstate_vmx_nested_state = {
     }
 };
 
+static bool svm_nested_state_needed(void *opaque)
+{
+    struct kvm_nested_state *nested_state = opaque;
+
+    /*
+     * HF_GUEST_MASK and HF2_GIF_MASK are already serialized
+     * via hflags and hflags2, all that's left is the opaque
+     * nested state blob.
+     */
+    return (nested_state->format == KVM_STATE_NESTED_FORMAT_SVM &&
+            nested_state->size > offsetof(struct kvm_nested_state, data));
+}
+
+static const VMStateDescription vmstate_svm_nested_state = {
+    .name = "cpu/kvm_nested_state/svm",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = svm_nested_state_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_U64(hdr.svm.vmcb_pa, struct kvm_nested_state),
+        VMSTATE_UINT8_ARRAY(data.svm[0].vmcb12,
+                            struct kvm_nested_state,
+                            KVM_STATE_NESTED_SVM_VMCB_SIZE),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static bool nested_state_needed(void *opaque)
 {
     X86CPU *cpu = opaque;
     CPUX86State *env = &cpu->env;
 
     return (env->nested_state &&
-            vmx_nested_state_needed(env->nested_state));
+            (vmx_nested_state_needed(env->nested_state) ||
+             svm_nested_state_needed(env->nested_state)));
 }
 
 static int nested_state_post_load(void *opaque, int version_id)
@@ -1139,6 +1167,7 @@ static const VMStateDescription vmstate_kvm_nested_state = {
     },
     .subsections = (const VMStateDescription*[]) {
         &vmstate_vmx_nested_state,
+        &vmstate_svm_nested_state,
         NULL
     }
 };