hw/mem: add sp-mem device for Specific Purpose Memory
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> Reviewed-by: Igor Mammedov <imammedo@redhat.com> Reviewed-by: David Hildenbrand (Arm) <david@kernel.org> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Message-ID: <20260623075051.3797975-2-FangSheng.Huang@amd.com>
fanhuang committed
Jun 23, 2026 at 15:50 UTC
e83b01083631544bec27cbb3a381420b1ac7dc38
4 files changed
+147
hw/mem/Kconfig
+4
@@ -16,3 +16,7 @@ config CXL_MEM_DEVICE
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bool
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default y if CXL
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select MEM_DEVICE
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+
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+config SP_MEM
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+ bool
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+ select MEM_DEVICE
hw/mem/meson.build
+1
@@ -4,6 +4,7 @@ mem_ss.add(when: 'CONFIG_DIMM', if_true: files('pc-dimm.c'))
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mem_ss.add(when: 'CONFIG_NPCM7XX', if_true: files('npcm7xx_mc.c'))
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mem_ss.add(when: 'CONFIG_NVDIMM', if_true: files('nvdimm.c'))
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mem_ss.add(when: 'CONFIG_CXL_MEM_DEVICE', if_true: files('cxl_type3.c'))
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+mem_ss.add(when: 'CONFIG_SP_MEM', if_true: files('sp-mem.c'))
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stub_ss.add(files('cxl_type3_stubs.c'))
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stub_ss.add(files('memory-device-stubs.c'))
hw/mem/sp-mem.c
new
+109
@@ -0,0 +1,109 @@
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+/*
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+ * Specific Purpose Memory (SPM) device
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+ *
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+ * Copyright (c) 2026 Advanced Micro Devices, Inc.
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+ *
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+ * Authors:
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+ * FangSheng Huang <FangSheng.Huang@amd.com>
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+ *
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+ * SPDX-License-Identifier: GPL-2.0-or-later
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+ */
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+
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+#include "qemu/osdep.h"
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+#include "qemu/module.h"
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+#include "qapi/error.h"
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+#include "hw/core/qdev-properties.h"
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+#include "hw/core/qdev.h"
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+#include "hw/mem/sp-mem.h"
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+#include "hw/mem/memory-device.h"
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+#include "system/hostmem.h"
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+
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+#define SP_MEM_MEMDEV_PROP "memdev"
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+#define SP_MEM_NODE_PROP "node"
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+#define SP_MEM_ADDR_PROP "addr"
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+
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+static const Property sp_mem_properties[] = {
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+ DEFINE_PROP_LINK(SP_MEM_MEMDEV_PROP, SpMemDevice, hostmem,
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+ TYPE_MEMORY_BACKEND, HostMemoryBackend *),
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+ DEFINE_PROP_UINT32(SP_MEM_NODE_PROP, SpMemDevice, node, 0),
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+ DEFINE_PROP_UINT64(SP_MEM_ADDR_PROP, SpMemDevice, addr, 0),
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+};
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+
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+static uint64_t sp_mem_get_addr(const MemoryDeviceState *md)
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+{
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+ return object_property_get_uint(OBJECT(md), SP_MEM_ADDR_PROP,
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+ &error_abort);
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+}
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+
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+static void sp_mem_set_addr(MemoryDeviceState *md, uint64_t addr,
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+ Error **errp)
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+{
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+ object_property_set_uint(OBJECT(md), SP_MEM_ADDR_PROP, addr, errp);
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+}
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+
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+static MemoryRegion *sp_mem_get_memory_region(MemoryDeviceState *md,
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+ Error **errp)
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+{
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+ SpMemDevice *spm = SP_MEM(md);
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+
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+ if (!spm->hostmem) {
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+ error_setg(errp, "'%s' property must be set", SP_MEM_MEMDEV_PROP);
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+ return NULL;
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+ }
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+ return host_memory_backend_get_memory(spm->hostmem);
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+}
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+
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+static void sp_mem_realize(DeviceState *dev, Error **errp)
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+{
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+ SpMemDevice *spm = SP_MEM(dev);
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+
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+ if (!spm->hostmem) {
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+ error_setg(errp, "'%s' property is required", SP_MEM_MEMDEV_PROP);
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+ return;
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+ }
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+ if (host_memory_backend_is_mapped(spm->hostmem)) {
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+ error_setg(errp, "memory backend '%s' is already in use",
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+ object_get_canonical_path_component(OBJECT(spm->hostmem)));
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+ return;
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+ }
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+ host_memory_backend_set_mapped(spm->hostmem, true);
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+}
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+
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+static void sp_mem_unrealize(DeviceState *dev)
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+{
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+ SpMemDevice *spm = SP_MEM(dev);
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+
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+ host_memory_backend_set_mapped(spm->hostmem, false);
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+}
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+
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+static void sp_mem_class_init(ObjectClass *oc, const void *data)
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+{
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+ DeviceClass *dc = DEVICE_CLASS(oc);
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+ MemoryDeviceClass *mdc = MEMORY_DEVICE_CLASS(oc);
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+
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+ dc->desc = "SPM (Specific Purpose Memory) device";
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+ dc->hotpluggable = false;
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+ dc->realize = sp_mem_realize;
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+ dc->unrealize = sp_mem_unrealize;
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+ device_class_set_props(dc, sp_mem_properties);
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+
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+ mdc->get_addr = sp_mem_get_addr;
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+ mdc->set_addr = sp_mem_set_addr;
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+ mdc->get_memory_region = sp_mem_get_memory_region;
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+ mdc->get_plugged_size = memory_device_get_region_size;
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+}
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+
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+static const TypeInfo sp_mem_types[] = {
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+ {
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+ .name = TYPE_SP_MEM,
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+ .parent = TYPE_DEVICE,
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+ .class_init = sp_mem_class_init,
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+ .instance_size = sizeof(SpMemDevice),
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+ .interfaces = (InterfaceInfo[]) {
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+ { TYPE_MEMORY_DEVICE },
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+ { }
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+ },
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+ },
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+};
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+
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+DEFINE_TYPES(sp_mem_types)
include/hw/mem/sp-mem.h
new
+33
@@ -0,0 +1,33 @@
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+/*
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+ * Specific Purpose Memory (SPM) device
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+ *
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+ * TYPE_MEMORY_DEVICE subclass for boot-time-only memory exposed to the
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+ * guest as an E820 SOFT_RESERVED range with a SRAT memory-affinity entry.
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+ *
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+ * Copyright (c) 2026 Advanced Micro Devices, Inc.
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+ *
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+ * Authors:
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+ * FangSheng Huang <FangSheng.Huang@amd.com>
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+ *
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+ * SPDX-License-Identifier: GPL-2.0-or-later
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+ */
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+
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+#ifndef QEMU_SP_MEM_H
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+#define QEMU_SP_MEM_H
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+
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+#include "hw/core/qdev.h"
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+#include "qom/object.h"
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+
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+#define TYPE_SP_MEM "sp-mem"
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+
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+OBJECT_DECLARE_SIMPLE_TYPE(SpMemDevice, SP_MEM)
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+
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+struct SpMemDevice {
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+ DeviceState parent_obj;
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+
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+ HostMemoryBackend *hostmem;
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+ uint32_t node;
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+ uint64_t addr;
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+};
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+
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+#endif /* QEMU_SP_MEM_H */