When the kvm file descriptor changes as a part of confidential guest reset,
some architecture specific setups including SEV/SEV-SNP/TDX specific setups
needs to be redone. These changes are implemented as a part of the
kvm_arch_on_vmfd_change() callback which was introduced previously.

Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 target/i386/kvm/kvm.c        | 82 ++++++++++++++++++++++++++----------
 target/i386/kvm/trace-events |  1 +
 2 files changed, 60 insertions(+), 23 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index e28ab18a14..e27ccff7a6 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -3269,14 +3269,52 @@ static int kvm_vm_enable_energy_msrs(KVMState *s)
     return 0;
 }
 
+static int xen_init_wrapper(MachineState *ms, KVMState *s);
+
 int kvm_arch_on_vmfd_change(MachineState *ms, KVMState *s)
 {
-    abort();
+    int ret;
+
+    ret = kvm_arch_init(ms, s);
+    if (ret < 0) {
+        return ret;
+    }
+
+    if (object_dynamic_cast(OBJECT(ms), TYPE_X86_MACHINE)) {
+        X86MachineState *x86ms = X86_MACHINE(ms);
+
+        if (x86_machine_is_smm_enabled(x86ms)) {
+            memory_listener_register(&smram_listener.listener,
+                                     &smram_address_space);
+        }
+        kvm_set_max_apic_id(x86ms->apic_id_limit);
+    }
+
+    trace_kvm_arch_on_vmfd_change();
+    return 0;
+}
+
+static int xen_init_wrapper(MachineState *ms, KVMState *s)
+{
+    int ret = 0;
+#ifdef CONFIG_XEN_EMU
+    if (!object_dynamic_cast(OBJECT(ms), TYPE_PC_MACHINE)) {
+        error_report("kvm: Xen support only available in PC machine");
+        return -ENOTSUP;
+    }
+    /* hyperv_enabled() doesn't work yet. */
+    uint32_t msr = XEN_HYPERCALL_MSR;
+    ret = kvm_xen_init(s, msr);
+#else
+    error_report("kvm: Xen support not enabled in qemu");
+    return -ENOTSUP;
+#endif
+    return ret;
 }
 
 bool kvm_arch_supports_vmfd_change(void)
 {
-    return false;
+    return true;
 }
 
 int kvm_arch_init(MachineState *ms, KVMState *s)
@@ -3284,6 +3322,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
     int ret;
     struct utsname utsname;
     Error *local_err = NULL;
+    static bool first = true;
 
     /*
      * Initialize confidential guest (SEV/TDX) context, if required
@@ -3312,21 +3351,10 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
     }
 
     if (s->xen_version) {
-#ifdef CONFIG_XEN_EMU
-        if (!object_dynamic_cast(OBJECT(ms), TYPE_PC_MACHINE)) {
-            error_report("kvm: Xen support only available in PC machine");
-            return -ENOTSUP;
-        }
-        /* hyperv_enabled() doesn't work yet. */
-        uint32_t msr = XEN_HYPERCALL_MSR;
-        ret = kvm_xen_init(s, msr);
+        ret = xen_init_wrapper(ms, s);
         if (ret < 0) {
             return ret;
         }
-#else
-        error_report("kvm: Xen support not enabled in qemu");
-        return -ENOTSUP;
-#endif
     }
 
     ret = kvm_get_supported_msrs(s);
@@ -3353,16 +3381,17 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         return ret;
     }
 
-    /* Tell fw_cfg to notify the BIOS to reserve the range. */
-    e820_add_entry(KVM_IDENTITY_BASE, 0x4000, E820_RESERVED);
-
+    if (first) {
+        /* Tell fw_cfg to notify the BIOS to reserve the range. */
+        e820_add_entry(KVM_IDENTITY_BASE, 0x4000, E820_RESERVED);
+    }
     ret = kvm_vm_set_nr_mmu_pages(s);
     if (ret < 0) {
         return ret;
     }
 
     if (object_dynamic_cast(OBJECT(ms), TYPE_X86_MACHINE) &&
-        x86_machine_is_smm_enabled(X86_MACHINE(ms))) {
+        x86_machine_is_smm_enabled(X86_MACHINE(ms)) && first) {
         smram_machine_done.notify = register_smram_listener;
         qemu_add_machine_init_done_notifier(&smram_machine_done);
     }
@@ -3409,15 +3438,22 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
                 return ret;
             }
 
-            ret = kvm_msr_energy_thread_init(s, ms);
-            if (ret < 0) {
-                error_report("kvm : error RAPL feature requirement not met");
-                return ret;
+            if (first) {
+                ret = kvm_msr_energy_thread_init(s, ms);
+                if (ret < 0) {
+                    error_report("kvm : "
+                                 "error RAPL feature requirement not met");
+                    return ret;
+                }
             }
         }
     }
 
-    kvm_vmfd_add_change_notifier(&kvm_vmfd_change_notifier);
+    if (first) {
+        kvm_vmfd_add_change_notifier(&kvm_vmfd_change_notifier);
+    }
+
+    first = false;
 
     return 0;
 }
diff --git a/target/i386/kvm/trace-events b/target/i386/kvm/trace-events
index 74a6234ff7..2d213c9f9b 100644
--- a/target/i386/kvm/trace-events
+++ b/target/i386/kvm/trace-events
@@ -6,6 +6,7 @@ kvm_x86_add_msi_route(int virq) "Adding route entry for virq %d"
 kvm_x86_remove_msi_route(int virq) "Removing route entry for virq %d"
 kvm_x86_update_msi_routes(int num) "Updated %d MSI routes"
 kvm_hc_map_gpa_range(uint64_t gpa, uint64_t size, uint64_t attributes, uint64_t flags) "gpa 0x%" PRIx64 " size 0x%" PRIx64 " attributes 0x%" PRIx64 " flags 0x%" PRIx64
+kvm_arch_on_vmfd_change(void) ""
 
 # xen-emu.c
 kvm_xen_hypercall(int cpu, uint8_t cpl, uint64_t input, uint64_t a0, uint64_t a1, uint64_t a2, uint64_t ret) "xen_hypercall: cpu %d cpl %d input %" PRIu64 " a0 0x%" PRIx64 " a1 0x%" PRIx64 " a2 0x%" PRIx64" ret 0x%" PRIx64
-- 
2.42.0