Merge tag 'mem-2024-12-21' of https://github.com/davidhildenbrand/qemu into staging

Hi,

"Host Memory Backends" and "Memory devices" queue ("mem"):
- Fixup handling of virtio-mem unplug during system resets, as
  preparation for s390x support (especially kdump in the Linux guest)
- virtio-mem support for s390x

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* tag 'mem-2024-12-21' of https://github.com/davidhildenbrand/qemu:
  s390x: virtio-mem support
  s390x/virtio-ccw: add support for virtio based memory devices
  s390x: remember the maximum page size
  s390x/pv: prepare for memory devices
  s390x/s390-virtio-ccw: prepare for memory devices
  s390x/s390-skeys: prepare for memory devices
  s390x/s390-stattrib-kvm: prepare for memory devices and sparse memory layouts
  s390x/s390-hypercall: introduce DIAG500 STORAGE_LIMIT
  s390x: introduce s390_get_memory_limit()
  s390x/s390-virtio-ccw: move setting the maximum guest size from sclp to machine code
  s390x: rename s390-virtio-hcall* to s390-hypercall*
  s390x/s390-virtio-hcall: prepare for more diag500 hypercalls
  s390x/s390-virtio-hcall: remove hypercall registration mechanism
  s390x/s390-virtio-ccw: don't crash on weird RAM sizes
  virtio-mem: unplug memory only during system resets, not device resets

Conflicts:
- hw/s390x/s390-stattrib-kvm.c
  sysemu/ -> system/ header rename conflict.
- hw/s390x/virtio-ccw-mem.c
  Make Property array const and removed DEFINE_PROP_END_OF_LIST() to
  conform to the latest conventions.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

2 files changed, 76 insertions, 32 deletions

diff --git a/hw/virtio/Kconfig b/hw/virtio/Kconfig
index 70c77e183d..7648a2d68d 100644
--- a/hw/virtio/Kconfig
+++ b/hw/virtio/Kconfig
@@ -29,6 +29,7 @@ config VIRTIO_MMIO
 config VIRTIO_CCW
     bool
     select VIRTIO
+    select VIRTIO_MD_SUPPORTED
 
 config VIRTIO_BALLOON
     bool
diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index cf362a4aa5..b1a003736b 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -61,6 +61,8 @@ static uint32_t virtio_mem_default_thp_size(void)
     } else if (qemu_real_host_page_size() == 64 * KiB) {
         default_thp_size = 512 * MiB;
     }
+#elif defined(__s390x__)
+    default_thp_size = 1 * MiB;
 #endif
 
     return default_thp_size;
@@ -168,7 +170,7 @@ static bool virtio_mem_has_shared_zeropage(RAMBlock *rb)
  * necessary (as the section size can change). But it's more likely that the
  * section size will rather get smaller and not bigger over time.
  */
-#if defined(TARGET_X86_64) || defined(TARGET_I386)
+#if defined(TARGET_X86_64) || defined(TARGET_I386) || defined(TARGET_S390X)
 #define VIRTIO_MEM_USABLE_EXTENT (2 * (128 * MiB))
 #elif defined(TARGET_ARM)
 #define VIRTIO_MEM_USABLE_EXTENT (2 * (512 * MiB))
@@ -956,6 +958,7 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
     VirtIOMEM *vmem = VIRTIO_MEM(dev);
     uint64_t page_size;
     RAMBlock *rb;
+    Object *obj;
     int ret;
 
     if (!vmem->memdev) {
@@ -1121,7 +1124,28 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
         vmstate_register_any(VMSTATE_IF(vmem),
                              &vmstate_virtio_mem_device_early, vmem);
     }
-    qemu_register_resettable(OBJECT(vmem));
+
+    /*
+     * We only want to unplug all memory to start with a clean slate when
+     * it is safe for the guest -- during system resets that call
+     * qemu_devices_reset().
+     *
+     * We'll filter out selected qemu_devices_reset() calls used for other
+     * purposes, like resetting all devices during wakeup from suspend on
+     * x86 based on the reset type passed to qemu_devices_reset().
+     *
+     * Unplugging all memory during simple device resets can result in the VM
+     * unexpectedly losing RAM, corrupting VM state.
+     *
+     * Simple device resets (or resets triggered by getting a parent device
+     * reset) must not change the state of plugged memory blocks. Therefore,
+     * we need a dedicated reset object that only gets called during
+     * qemu_devices_reset().
+     */
+    obj = object_new(TYPE_VIRTIO_MEM_SYSTEM_RESET);
+    vmem->system_reset = VIRTIO_MEM_SYSTEM_RESET(obj);
+    vmem->system_reset->vmem = vmem;
+    qemu_register_resettable(obj);
 
     /*
      * Set ourselves as RamDiscardManager before the plug handler maps the
@@ -1141,7 +1165,10 @@ static void virtio_mem_device_unrealize(DeviceState *dev)
      * found via an address space anymore. Unset ourselves.
      */
     memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL);
-    qemu_unregister_resettable(OBJECT(vmem));
+
+    qemu_unregister_resettable(OBJECT(vmem->system_reset));
+    object_unref(OBJECT(vmem->system_reset));
+
     if (vmem->early_migration) {
         vmstate_unregister(VMSTATE_IF(vmem), &vmstate_virtio_mem_device_early,
                            vmem);
@@ -1840,38 +1867,12 @@ static void virtio_mem_unplug_request_check(VirtIOMEM *vmem, Error **errp)
     }
 }
 
-static ResettableState *virtio_mem_get_reset_state(Object *obj)
-{
-    VirtIOMEM *vmem = VIRTIO_MEM(obj);
-    return &vmem->reset_state;
-}
-
-static void virtio_mem_system_reset_hold(Object *obj, ResetType type)
-{
-    VirtIOMEM *vmem = VIRTIO_MEM(obj);
-
-    /*
-     * When waking up from standby/suspend-to-ram, do not unplug any memory.
-     */
-    if (type == RESET_TYPE_WAKEUP) {
-        return;
-    }
-
-    /*
-     * During usual resets, we will unplug all memory and shrink the usable
-     * region size. This is, however, not possible in all scenarios. Then,
-     * the guest has to deal with this manually (VIRTIO_MEM_REQ_UNPLUG_ALL).
-     */
-    virtio_mem_unplug_all(vmem);
-}
-
 static void virtio_mem_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
     VirtIOMEMClass *vmc = VIRTIO_MEM_CLASS(klass);
     RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_CLASS(klass);
-    ResettableClass *rc = RESETTABLE_CLASS(klass);
 
     device_class_set_props(dc, virtio_mem_properties);
     dc->vmsd = &vmstate_virtio_mem;
@@ -1898,9 +1899,6 @@ static void virtio_mem_class_init(ObjectClass *klass, void *data)
     rdmc->replay_discarded = virtio_mem_rdm_replay_discarded;
     rdmc->register_listener = virtio_mem_rdm_register_listener;
     rdmc->unregister_listener = virtio_mem_rdm_unregister_listener;
-
-    rc->get_state = virtio_mem_get_reset_state;
-    rc->phases.hold = virtio_mem_system_reset_hold;
 }
 
 static const TypeInfo virtio_mem_info = {
@@ -1923,3 +1921,48 @@ static void virtio_register_types(void)
 }
 
 type_init(virtio_register_types)
+
+OBJECT_DEFINE_SIMPLE_TYPE_WITH_INTERFACES(VirtioMemSystemReset, virtio_mem_system_reset, VIRTIO_MEM_SYSTEM_RESET, OBJECT, { TYPE_RESETTABLE_INTERFACE }, { })
+
+static void virtio_mem_system_reset_init(Object *obj)
+{
+}
+
+static void virtio_mem_system_reset_finalize(Object *obj)
+{
+}
+
+static ResettableState *virtio_mem_system_reset_get_state(Object *obj)
+{
+    VirtioMemSystemReset *vmem_reset = VIRTIO_MEM_SYSTEM_RESET(obj);
+
+    return &vmem_reset->reset_state;
+}
+
+static void virtio_mem_system_reset_hold(Object *obj, ResetType type)
+{
+    VirtioMemSystemReset *vmem_reset = VIRTIO_MEM_SYSTEM_RESET(obj);
+    VirtIOMEM *vmem = vmem_reset->vmem;
+
+    /*
+     * When waking up from standby/suspend-to-ram, do not unplug any memory.
+     */
+    if (type == RESET_TYPE_WAKEUP) {
+        return;
+    }
+
+    /*
+     * During usual resets, we will unplug all memory and shrink the usable
+     * region size. This is, however, not possible in all scenarios. Then,
+     * the guest has to deal with this manually (VIRTIO_MEM_REQ_UNPLUG_ALL).
+     */
+    virtio_mem_unplug_all(vmem);
+}
+
+static void virtio_mem_system_reset_class_init(ObjectClass *klass, void *data)
+{
+    ResettableClass *rc = RESETTABLE_CLASS(klass);
+
+    rc->get_state = virtio_mem_system_reset_get_state;
+    rc->phases.hold = virtio_mem_system_reset_hold;
+}