This change adds common kvm specific support to handle KVM VM file descriptor
change. KVM VM file descriptor can change as a part of confidential guest reset
mechanism. A new function api kvm_arch_on_vmfd_change() per
architecture platform is added in order to implement architecture specific
changes required to support it. A subsequent patch will add x86 specific
implementation for kvm_arch_on_vmfd_change() as currently only x86 supports
confidential guest reset.

Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 MAINTAINERS            |  6 ++++
 accel/kvm/kvm-all.c    | 80 ++++++++++++++++++++++++++++++++++++++++--
 accel/kvm/trace-events |  1 +
 include/system/kvm.h   |  3 ++
 stubs/kvm.c            | 22 ++++++++++++
 stubs/meson.build      |  1 +
 target/i386/kvm/kvm.c  | 10 ++++++
 7 files changed, 120 insertions(+), 3 deletions(-)
 create mode 100644 stubs/kvm.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 65ac60b86b..a88901a7d7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -152,6 +152,12 @@ F: tools/i386/
 F: tests/functional/i386/
 F: tests/functional/x86_64/
 
+X86 VM file descriptor change on reset test
+M: Ani Sinha <anisinha@redhat.com>
+M: Paolo Bonzini <pbonzini@redhat.com>
+S: Maintained
+F: stubs/kvm.c
+
 Guest CPU cores (TCG)
 ---------------------
 Overall TCG CPUs
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 8301a512e7..46243cfcf2 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2415,11 +2415,9 @@ void kvm_irqchip_set_qemuirq_gsi(KVMState *s, qemu_irq irq, int gsi)
     g_hash_table_insert(s->gsimap, irq, GINT_TO_POINTER(gsi));
 }
 
-static void kvm_irqchip_create(KVMState *s)
+static void do_kvm_irqchip_create(KVMState *s)
 {
     int ret;
-
-    assert(s->kernel_irqchip_split != ON_OFF_AUTO_AUTO);
     if (kvm_check_extension(s, KVM_CAP_IRQCHIP)) {
         ;
     } else if (kvm_check_extension(s, KVM_CAP_S390_IRQCHIP)) {
@@ -2452,7 +2450,13 @@ static void kvm_irqchip_create(KVMState *s)
         fprintf(stderr, "Create kernel irqchip failed: %s\n", strerror(-ret));
         exit(1);
     }
+}
 
+static void kvm_irqchip_create(KVMState *s)
+{
+    assert(s->kernel_irqchip_split != ON_OFF_AUTO_AUTO);
+
+    do_kvm_irqchip_create(s);
     kvm_kernel_irqchip = true;
     /* If we have an in-kernel IRQ chip then we must have asynchronous
      * interrupt delivery (though the reverse is not necessarily true)
@@ -2607,6 +2611,75 @@ static int kvm_setup_dirty_ring(KVMState *s)
     return 0;
 }
 
+static int kvm_reset_vmfd(MachineState *ms)
+{
+    KVMState *s;
+    KVMMemoryListener *kml;
+    int ret = 0, type;
+    Error *err = NULL;
+
+    /*
+     * bail if the current architecture does not support VM file
+     * descriptor change.
+     */
+    if (!kvm_arch_supports_vmfd_change()) {
+        error_report("This target architecture does not support KVM VM "
+                     "file descriptor change.");
+        return -EOPNOTSUPP;
+    }
+
+    s = KVM_STATE(ms->accelerator);
+    kml = &s->memory_listener;
+
+    memory_listener_unregister(&kml->listener);
+    memory_listener_unregister(&kvm_io_listener);
+
+    if (s->vmfd >= 0) {
+        close(s->vmfd);
+    }
+
+    type = find_kvm_machine_type(ms);
+    if (type < 0) {
+        return -EINVAL;
+    }
+
+    ret = do_kvm_create_vm(s, type);
+    if (ret < 0) {
+        return ret;
+    }
+
+    s->vmfd = ret;
+
+    kvm_setup_dirty_ring(s);
+
+    /* rebind memory to new vm fd */
+    ret = ram_block_rebind(&err);
+    if (ret < 0) {
+        return ret;
+    }
+    assert(!err);
+
+    ret = kvm_arch_on_vmfd_change(ms, s);
+    if (ret < 0) {
+        return ret;
+    }
+
+    if (s->kernel_irqchip_allowed) {
+        do_kvm_irqchip_create(s);
+    }
+
+    /* these can be only called after ram_block_rebind() */
+    memory_listener_register(&kml->listener, &address_space_memory);
+    memory_listener_register(&kvm_io_listener, &address_space_io);
+
+    /*
+     * kvm fd has changed. Commit the irq routes to KVM once more.
+     */
+    kvm_irqchip_commit_routes(s);
+    trace_kvm_reset_vmfd();
+    return ret;
+}
+
 static int kvm_init(AccelState *as, MachineState *ms)
 {
     MachineClass *mc = MACHINE_GET_CLASS(ms);
@@ -4014,6 +4087,7 @@ static void kvm_accel_class_init(ObjectClass *oc, const void *data)
     AccelClass *ac = ACCEL_CLASS(oc);
     ac->name = "KVM";
     ac->init_machine = kvm_init;
+    ac->reset_vmfd = kvm_reset_vmfd;
     ac->has_memory = kvm_accel_has_memory;
     ac->allowed = &kvm_allowed;
     ac->gdbstub_supported_sstep_flags = kvm_gdbstub_sstep_flags;
diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events
index e43d18a869..e4beda0148 100644
--- a/accel/kvm/trace-events
+++ b/accel/kvm/trace-events
@@ -14,6 +14,7 @@ kvm_destroy_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d id: %lu"
 kvm_park_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d id: %lu"
 kvm_unpark_vcpu(unsigned long arch_cpu_id, const char *msg) "id: %lu %s"
 kvm_irqchip_commit_routes(void) ""
+kvm_reset_vmfd(void) ""
 kvm_irqchip_add_msi_route(char *name, int vector, int virq) "dev %s vector %d virq %d"
 kvm_irqchip_update_msi_route(int virq) "Updating MSI route virq=%d"
 kvm_irqchip_release_virq(int virq) "virq %d"
diff --git a/include/system/kvm.h b/include/system/kvm.h
index 8f9eecf044..5fc7251fd9 100644
--- a/include/system/kvm.h
+++ b/include/system/kvm.h
@@ -456,6 +456,9 @@ int kvm_physical_memory_addr_from_host(KVMState *s, void *ram_addr,
 
 #endif /* COMPILING_PER_TARGET */
 
+bool kvm_arch_supports_vmfd_change(void);
+int kvm_arch_on_vmfd_change(MachineState *ms, KVMState *s);
+
 void kvm_cpu_synchronize_state(CPUState *cpu);
 
 void kvm_init_cpu_signals(CPUState *cpu);
diff --git a/stubs/kvm.c b/stubs/kvm.c
new file mode 100644
index 0000000000..2db61d89a7
--- /dev/null
+++ b/stubs/kvm.c
@@ -0,0 +1,22 @@
+/*
+ * kvm target arch specific stubs
+ *
+ * Copyright (c) 2026 Red Hat, Inc.
+ *
+ * Author:
+ *   Ani Sinha <anisinha@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include "qemu/osdep.h"
+#include "system/kvm.h"
+
+int kvm_arch_on_vmfd_change(MachineState *ms, KVMState *s)
+{
+    abort();
+}
+
+bool kvm_arch_supports_vmfd_change(void)
+{
+    return false;
+}
diff --git a/stubs/meson.build b/stubs/meson.build
index 8a07059500..6ae478bacc 100644
--- a/stubs/meson.build
+++ b/stubs/meson.build
@@ -74,6 +74,7 @@ if have_system
   if igvm.found()
     stub_ss.add(files('igvm.c'))
   endif
+  stub_ss.add(files('kvm.c'))
   stub_ss.add(files('target-get-monitor-def.c'))
   stub_ss.add(files('target-monitor-defs.c'))
   stub_ss.add(files('win32-kbd-hook.c'))
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index da1ed3b62a..83c15f098e 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -3252,6 +3252,16 @@ static int kvm_vm_enable_energy_msrs(KVMState *s)
     return 0;
 }
 
+int kvm_arch_on_vmfd_change(MachineState *ms, KVMState *s)
+{
+    abort();
+}
+
+bool kvm_arch_supports_vmfd_change(void)
+{
+    return false;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     int ret;
-- 
2.42.0