From: Magnus Kulke <magnuskulke@linux.microsoft.com>

Add memory listener hooks for the MSHV accelerator to track guest
memory regions. This enables the backend to respond to region
additions, removals and will be used to manage guest memory mappings
inside the hypervisor.

Actually registering physical memory in the hypervisor is still stubbed
out.

Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250916164847.77883-9-magnuskulke@linux.microsoft.com
[mshv.h/mshv_int.h split. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/system/mshv_int.h |  4 +++
 accel/mshv/mem.c          | 25 +++++++++++++++
 accel/mshv/mshv-all.c     | 67 +++++++++++++++++++++++++++++++++++++--
 accel/mshv/meson.build    |  1 +
 4 files changed, 95 insertions(+), 2 deletions(-)
 create mode 100644 accel/mshv/mem.c

diff --git a/include/system/mshv_int.h b/include/system/mshv_int.h
index 132491b599d..cfa177ff72f 100644
--- a/include/system/mshv_int.h
+++ b/include/system/mshv_int.h
@@ -38,4 +38,8 @@ struct MshvState {
     MshvAddressSpace *as;
 };
 
+/* memory */
+void mshv_set_phys_mem(MshvMemoryListener *mml, MemoryRegionSection *section,
+                       bool add);
+
 #endif
diff --git a/accel/mshv/mem.c b/accel/mshv/mem.c
new file mode 100644
index 00000000000..9889918c31f
--- /dev/null
+++ b/accel/mshv/mem.c
@@ -0,0 +1,25 @@
+/*
+ * QEMU MSHV support
+ *
+ * Copyright Microsoft, Corp. 2025
+ *
+ * Authors:
+ *  Magnus Kulke      <magnuskulke@microsoft.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "system/address-spaces.h"
+#include "system/mshv.h"
+#include "system/mshv_int.h"
+
+void mshv_set_phys_mem(MshvMemoryListener *mml, MemoryRegionSection *section,
+                       bool add)
+{
+    error_report("unimplemented");
+    abort();
+}
+
diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
index ae12f0f58b9..a684a366775 100644
--- a/accel/mshv/mshv-all.c
+++ b/accel/mshv/mshv-all.c
@@ -49,10 +49,73 @@ bool mshv_allowed;
 
 MshvState *mshv_state;
 
+static void mem_region_add(MemoryListener *listener,
+                           MemoryRegionSection *section)
+{
+    MshvMemoryListener *mml;
+    mml = container_of(listener, MshvMemoryListener, listener);
+    memory_region_ref(section->mr);
+    mshv_set_phys_mem(mml, section, true);
+}
+
+static void mem_region_del(MemoryListener *listener,
+                           MemoryRegionSection *section)
+{
+    MshvMemoryListener *mml;
+    mml = container_of(listener, MshvMemoryListener, listener);
+    mshv_set_phys_mem(mml, section, false);
+    memory_region_unref(section->mr);
+}
+
+static MemoryListener mshv_memory_listener = {
+    .name = "mshv",
+    .priority = MEMORY_LISTENER_PRIORITY_ACCEL,
+    .region_add = mem_region_add,
+    .region_del = mem_region_del,
+};
+
+static MemoryListener mshv_io_listener = {
+    .name = "mshv", .priority = MEMORY_LISTENER_PRIORITY_DEV_BACKEND,
+    /* MSHV does not support PIO eventfd */
+};
+
+static void register_mshv_memory_listener(MshvState *s, MshvMemoryListener *mml,
+                                          AddressSpace *as, int as_id,
+                                          const char *name)
+{
+    int i;
+
+    mml->listener = mshv_memory_listener;
+    mml->listener.name = name;
+    memory_listener_register(&mml->listener, as);
+    for (i = 0; i < s->nr_as; ++i) {
+        if (!s->as[i].as) {
+            s->as[i].as = as;
+            s->as[i].ml = mml;
+            break;
+        }
+    }
+}
+
 static int mshv_init(AccelState *as, MachineState *ms)
 {
-    error_report("unimplemented");
-    abort();
+    MshvState *s;
+    s = MSHV_STATE(as);
+
+    accel_blocker_init();
+
+    s->vm = 0;
+
+    s->nr_as = 1;
+    s->as = g_new0(MshvAddressSpace, s->nr_as);
+
+    mshv_state = s;
+
+    register_mshv_memory_listener(s, &s->memory_listener, &address_space_memory,
+                                  0, "mshv-memory");
+    memory_listener_register(&mshv_io_listener, &address_space_io);
+
+    return 0;
 }
 
 static void mshv_start_vcpu_thread(CPUState *cpu)
diff --git a/accel/mshv/meson.build b/accel/mshv/meson.build
index 4c03ac79219..8a6beb3fb1e 100644
--- a/accel/mshv/meson.build
+++ b/accel/mshv/meson.build
@@ -1,5 +1,6 @@
 mshv_ss = ss.source_set()
 mshv_ss.add(if_true: files(
+  'mem.c',
   'mshv-all.c'
 ))
 
-- 
2.51.0