[PATCH v13 01/10] hw/mem: add sp-mem device for Specific Purpose Memory

[fanhuang <FangSheng.Huang@amd.com>]

Introduce a TYPE_MEMORY_DEVICE subclass `sp-mem` for boot-time
SOFT_RESERVED memory exposed to the guest with a per-device NUMA
proximity domain.

The device targets accelerator memory (HBM and similar) that the
firmware hands to the guest OS as SOFT_RESERVED memory, so a driver
in the guest -- rather than the kernel's general allocator -- owns
the range.

Usage:

    -object memory-backend-ram,id=spm0,size=$SIZE
    -numa node,nodeid=$N
    -device sp-mem,id=dev0,memdev=spm0,node=$N[,addr=$GPA]

The device is boot-time only (no hotplug).

Signed-off-by: FangSheng Huang <FangSheng.Huang@amd.com>
---
 include/hw/mem/sp-mem.h |  33 ++++++++++++
 hw/mem/sp-mem.c         | 109 ++++++++++++++++++++++++++++++++++++++++
 hw/mem/Kconfig          |   4 ++
 hw/mem/meson.build      |   1 +
 4 files changed, 147 insertions(+)
 create mode 100644 include/hw/mem/sp-mem.h
 create mode 100644 hw/mem/sp-mem.c

diff --git a/include/hw/mem/sp-mem.h b/include/hw/mem/sp-mem.h
new file mode 100644
index 0000000000..a8951b49e6
--- /dev/null
+++ b/include/hw/mem/sp-mem.h
@@ -0,0 +1,33 @@
+/*
+ * Specific Purpose Memory (SPM) device
+ *
+ * TYPE_MEMORY_DEVICE subclass for boot-time-only memory exposed to the
+ * guest as an E820 SOFT_RESERVED range with a SRAT memory-affinity entry.
+ *
+ * Copyright (c) 2026 Advanced Micro Devices, Inc.
+ *
+ * Authors:
+ *  FangSheng Huang <FangSheng.Huang@amd.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef QEMU_SP_MEM_H
+#define QEMU_SP_MEM_H
+
+#include "hw/core/qdev.h"
+#include "qom/object.h"
+
+#define TYPE_SP_MEM "sp-mem"
+
+OBJECT_DECLARE_SIMPLE_TYPE(SpMemDevice, SP_MEM)
+
+struct SpMemDevice {
+    DeviceState parent_obj;
+
+    HostMemoryBackend *hostmem;
+    uint32_t node;
+    uint64_t addr;
+};
+
+#endif /* QEMU_SP_MEM_H */
diff --git a/hw/mem/sp-mem.c b/hw/mem/sp-mem.c
new file mode 100644
index 0000000000..d088222f54
--- /dev/null
+++ b/hw/mem/sp-mem.c
@@ -0,0 +1,109 @@
+/*
+ * Specific Purpose Memory (SPM) device
+ *
+ * Copyright (c) 2026 Advanced Micro Devices, Inc.
+ *
+ * Authors:
+ *  FangSheng Huang <FangSheng.Huang@amd.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/module.h"
+#include "qapi/error.h"
+#include "hw/core/qdev-properties.h"
+#include "hw/core/qdev.h"
+#include "hw/mem/sp-mem.h"
+#include "hw/mem/memory-device.h"
+#include "system/hostmem.h"
+
+#define SP_MEM_MEMDEV_PROP    "memdev"
+#define SP_MEM_NODE_PROP      "node"
+#define SP_MEM_ADDR_PROP      "addr"
+
+static const Property sp_mem_properties[] = {
+    DEFINE_PROP_LINK(SP_MEM_MEMDEV_PROP, SpMemDevice, hostmem,
+                     TYPE_MEMORY_BACKEND, HostMemoryBackend *),
+    DEFINE_PROP_UINT32(SP_MEM_NODE_PROP, SpMemDevice, node, 0),
+    DEFINE_PROP_UINT64(SP_MEM_ADDR_PROP, SpMemDevice, addr, 0),
+};
+
+static uint64_t sp_mem_get_addr(const MemoryDeviceState *md)
+{
+    return object_property_get_uint(OBJECT(md), SP_MEM_ADDR_PROP,
+                                    &error_abort);
+}
+
+static void sp_mem_set_addr(MemoryDeviceState *md, uint64_t addr,
+                            Error **errp)
+{
+    object_property_set_uint(OBJECT(md), SP_MEM_ADDR_PROP, addr, errp);
+}
+
+static MemoryRegion *sp_mem_get_memory_region(MemoryDeviceState *md,
+                                              Error **errp)
+{
+    SpMemDevice *spm = SP_MEM(md);
+
+    if (!spm->hostmem) {
+        error_setg(errp, "'%s' property must be set", SP_MEM_MEMDEV_PROP);
+        return NULL;
+    }
+    return host_memory_backend_get_memory(spm->hostmem);
+}
+
+static void sp_mem_realize(DeviceState *dev, Error **errp)
+{
+    SpMemDevice *spm = SP_MEM(dev);
+
+    if (!spm->hostmem) {
+        error_setg(errp, "'%s' property is required", SP_MEM_MEMDEV_PROP);
+        return;
+    }
+    if (host_memory_backend_is_mapped(spm->hostmem)) {
+        error_setg(errp, "memory backend '%s' is already in use",
+                   object_get_canonical_path_component(OBJECT(spm->hostmem)));
+        return;
+    }
+    host_memory_backend_set_mapped(spm->hostmem, true);
+}
+
+static void sp_mem_unrealize(DeviceState *dev)
+{
+    SpMemDevice *spm = SP_MEM(dev);
+
+    host_memory_backend_set_mapped(spm->hostmem, false);
+}
+
+static void sp_mem_class_init(ObjectClass *oc, const void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(oc);
+    MemoryDeviceClass *mdc = MEMORY_DEVICE_CLASS(oc);
+
+    dc->desc = "SPM (Specific Purpose Memory) device";
+    dc->hotpluggable = false;
+    dc->realize = sp_mem_realize;
+    dc->unrealize = sp_mem_unrealize;
+    device_class_set_props(dc, sp_mem_properties);
+
+    mdc->get_addr            = sp_mem_get_addr;
+    mdc->set_addr            = sp_mem_set_addr;
+    mdc->get_memory_region   = sp_mem_get_memory_region;
+    mdc->get_plugged_size    = memory_device_get_region_size;
+}
+
+static const TypeInfo sp_mem_types[] = {
+    {
+        .name          = TYPE_SP_MEM,
+        .parent        = TYPE_DEVICE,
+        .class_init    = sp_mem_class_init,
+        .instance_size = sizeof(SpMemDevice),
+        .interfaces    = (InterfaceInfo[]) {
+            { TYPE_MEMORY_DEVICE },
+            { }
+        },
+    },
+};
+
+DEFINE_TYPES(sp_mem_types)
diff --git a/hw/mem/Kconfig b/hw/mem/Kconfig
index 73c5ae8ad9..39ddb36710 100644
--- a/hw/mem/Kconfig
+++ b/hw/mem/Kconfig
@@ -16,3 +16,7 @@ config CXL_MEM_DEVICE
     bool
     default y if CXL
     select MEM_DEVICE
+
+config SP_MEM
+    bool
+    select MEM_DEVICE
diff --git a/hw/mem/meson.build b/hw/mem/meson.build
index 8c2beeb7d4..f410d75475 100644
--- a/hw/mem/meson.build
+++ b/hw/mem/meson.build
@@ -4,6 +4,7 @@ mem_ss.add(when: 'CONFIG_DIMM', if_true: files('pc-dimm.c'))
 mem_ss.add(when: 'CONFIG_NPCM7XX', if_true: files('npcm7xx_mc.c'))
 mem_ss.add(when: 'CONFIG_NVDIMM', if_true: files('nvdimm.c'))
 mem_ss.add(when: 'CONFIG_CXL_MEM_DEVICE', if_true: files('cxl_type3.c'))
+mem_ss.add(when: 'CONFIG_SP_MEM', if_true: files('sp-mem.c'))
 stub_ss.add(files('cxl_type3_stubs.c'))
 
 stub_ss.add(files('memory-device-stubs.c'))
-- 
2.34.1