[PATCH 2/3] hw/misc: Add mmio-debug-exit device

[Ilya Leoshkevich <iii@linux.ibm.com>]

System tests on x86 use isa-debug-exit device in order to signal
success or failure to the test runner. Unfortunately it's not easily
usable on other architectures, since a guest needs to access
address_space_io, which may not be as straightforward as on x86.
Also, it requires adding ISA bus, which an architecture might not
otherwise need.

Introduce mmio-debug-exit device, which has the same semantics, but is
triggered by writes to memory.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 hw/misc/Kconfig          |  3 ++
 hw/misc/debugexit_mmio.c | 80 ++++++++++++++++++++++++++++++++++++++++
 hw/misc/meson.build      |  1 +
 hw/s390x/Kconfig         |  1 +
 4 files changed, 85 insertions(+)
 create mode 100644 hw/misc/debugexit_mmio.c

diff --git a/hw/misc/Kconfig b/hw/misc/Kconfig
index cbabe9f78c..0f12735ef7 100644
--- a/hw/misc/Kconfig
+++ b/hw/misc/Kconfig
@@ -15,6 +15,9 @@ config ISA_DEBUG
     bool
     depends on ISA_BUS
 
+config MMIO_DEBUGEXIT
+    bool
+
 config SGA
     bool
     depends on ISA_BUS
diff --git a/hw/misc/debugexit_mmio.c b/hw/misc/debugexit_mmio.c
new file mode 100644
index 0000000000..5e823cc01c
--- /dev/null
+++ b/hw/misc/debugexit_mmio.c
@@ -0,0 +1,80 @@
+/*
+ * Exit with status X when the guest writes X (little-endian) to a specified
+ * address. For testing purposes only.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "exec/address-spaces.h"
+#include "exec/memory.h"
+#include "hw/qdev-core.h"
+#include "hw/qdev-properties.h"
+
+#define TYPE_MMIO_DEBUG_EXIT_DEVICE "mmio-debug-exit"
+OBJECT_DECLARE_SIMPLE_TYPE(MMIODebugExitState, MMIO_DEBUG_EXIT_DEVICE)
+
+struct MMIODebugExitState {
+    DeviceState parent_obj;
+
+    uint32_t base;
+    uint32_t size;
+    MemoryRegion region;
+};
+
+static uint64_t mmio_debug_exit_read(void *opaque, hwaddr addr, unsigned size)
+{
+    return 0;
+}
+
+static void mmio_debug_exit_write(void *opaque, hwaddr addr, uint64_t val,
+                                  unsigned width)
+{
+    exit(val);
+}
+
+static const MemoryRegionOps mmio_debug_exit_ops = {
+    .read = mmio_debug_exit_read,
+    .write = mmio_debug_exit_write,
+    .valid.min_access_size = 1,
+    .valid.max_access_size = 8,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+};
+
+static void mmio_debug_exit_realizefn(DeviceState *d, Error **errp)
+{
+    MMIODebugExitState *s = MMIO_DEBUG_EXIT_DEVICE(d);
+
+    memory_region_init_io(&s->region, OBJECT(s), &mmio_debug_exit_ops, s,
+                          TYPE_MMIO_DEBUG_EXIT_DEVICE, s->size);
+    memory_region_add_subregion(get_system_memory(), s->base, &s->region);
+}
+
+static Property mmio_debug_exit_properties[] = {
+    DEFINE_PROP_UINT32("base", MMIODebugExitState, base, 0),
+    DEFINE_PROP_UINT32("size", MMIODebugExitState, size, 1),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void mmio_debug_exit_class_initfn(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = mmio_debug_exit_realizefn;
+    device_class_set_props(dc, mmio_debug_exit_properties);
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+}
+
+static const TypeInfo mmio_debug_exit_info = {
+    .name          = TYPE_MMIO_DEBUG_EXIT_DEVICE,
+    .parent        = TYPE_DEVICE,
+    .instance_size = sizeof(MMIODebugExitState),
+    .class_init    = mmio_debug_exit_class_initfn,
+};
+
+static void mmio_debug_exit_register_types(void)
+{
+    type_register_static(&mmio_debug_exit_info);
+}
+
+type_init(mmio_debug_exit_register_types)
diff --git a/hw/misc/meson.build b/hw/misc/meson.build
index 95268eddc0..1d2a1067dc 100644
--- a/hw/misc/meson.build
+++ b/hw/misc/meson.build
@@ -2,6 +2,7 @@ softmmu_ss.add(when: 'CONFIG_APPLESMC', if_true: files('applesmc.c'))
 softmmu_ss.add(when: 'CONFIG_EDU', if_true: files('edu.c'))
 softmmu_ss.add(when: 'CONFIG_FW_CFG_DMA', if_true: files('vmcoreinfo.c'))
 softmmu_ss.add(when: 'CONFIG_ISA_DEBUG', if_true: files('debugexit.c'))
+softmmu_ss.add(when: 'CONFIG_MMIO_DEBUGEXIT', if_true: files('debugexit_mmio.c'))
 softmmu_ss.add(when: 'CONFIG_ISA_TESTDEV', if_true: files('pc-testdev.c'))
 softmmu_ss.add(when: 'CONFIG_PCA9552', if_true: files('pca9552.c'))
 softmmu_ss.add(when: 'CONFIG_PCI_TESTDEV', if_true: files('pci-testdev.c'))
diff --git a/hw/s390x/Kconfig b/hw/s390x/Kconfig
index 5e7d8a2bae..9223715dcc 100644
--- a/hw/s390x/Kconfig
+++ b/hw/s390x/Kconfig
@@ -5,6 +5,7 @@ config S390_CCW_VIRTIO
     imply VFIO_AP
     imply VFIO_CCW
     imply WDT_DIAG288
+    imply MMIO_DEBUGEXIT
     select PCI
     select S390_FLIC
     select SCLPCONSOLE
-- 
2.35.3