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 <[email protected]>
---
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 <[email protected]>
+ *
+ * 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 <[email protected]>
+ *
+ * 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
