This series adds a TYPE_MEMORY_DEVICE subclass `sp-mem` for boot-time
SOFT_RESERVED guest memory, following the direction from the v7
thread [1] and the v8 / v9 / v10 / v11 reviews [2][3][4][5].
Background
----------
This series targets coherent CPU + accelerator shared-address-space
systems, where the accelerator's HBM is not a device-private
framebuffer behind a PCIe BAR but a tier of host system memory:
visible to the CPU in the platform physical address space, shared
coherently with the accelerator over the platform fabric, and bound
to a NUMA proximity domain set by platform firmware at boot fabric
training.
For such a region to function correctly in the guest, two things
must hold simultaneously: the CPU memory subsystem has to see it in
the system memory map (so the CPU side can address it), and it has
to be reserved exclusively for the accelerator's driver (so the
kernel's general allocator does not hand SPM pages to unrelated
workloads). The SOFT_RESERVED memory type in E820 plus a matching
SRAT memory-affinity entry is the mechanism that delivers both: a
firmware-produced topology that the CPU memory subsystem honors and
the accelerator's driver consumes for its own range.
Approach
--------
The series introduces a new TYPE_MEMORY_DEVICE subclass `sp-mem`.
Each instance binds one host memory backend to a single NUMA
proximity domain and is boot-time only; placement, mapped-state
enforcement, and QMP introspection come from the existing
memory-device framework.
Testing
-------
Verified end-to-end on q35 + KVM, with both SeaBIOS and OVMF, for:
- single sp-mem instance
- two sp-mem instances on different NUMA nodes
Guest observations: /proc/iomem shows one SOFT_RESERVED entry per
sp-mem device, dmesg SRAT parsing reports the matching
memory_affinity entries with correct PXM, and the umbrella
HOTPLUGGABLE entry covers the remaining hotplug-memory window
without overlapping the sp-mem ranges.
Changes since v11
-----------------
- Drop the unneeded memory-device.h and system/hostmem.h includes
from sp-mem.h (HostMemoryBackend is forward-declared).
- Use SP_MEM_MEMDEV_PROP in sp_mem_get_memory_region()'s error
message, matching realize().
- Move the .unmigratable comment next to the field it documents.
All v11 patch-1 review comments from Philippe; patches 2-4 unchanged.
Patch 4 (MAINTAINERS) retains the Acked-by from Igor and David.
Previous versions
-----------------
v1:
https://lore.kernel.org/qemu-devel/[email protected]/
v2:
https://lore.kernel.org/qemu-devel/[email protected]/
v3:
https://lore.kernel.org/qemu-devel/[email protected]/
v4:
https://lore.kernel.org/qemu-devel/[email protected]/
v5:
https://lore.kernel.org/qemu-devel/[email protected]/
v6:
https://lore.kernel.org/qemu-devel/[email protected]/
v7:
https://lore.kernel.org/qemu-devel/[email protected]/
v8:
https://lore.kernel.org/qemu-devel/[email protected]/
v9:
https://lore.kernel.org/qemu-devel/[email protected]/
v10:
https://lore.kernel.org/qemu-devel/[email protected]/
v11:
https://lore.kernel.org/qemu-devel/[email protected]/
[1] v7 thread closeout:
https://lore.kernel.org/qemu-devel/[email protected]/
[2] v8 review:
https://lore.kernel.org/qemu-devel/20260601105057.2d764e55@imammedo/
[3] v9 review:
https://lore.kernel.org/qemu-devel/[email protected]/T/
[4] v10 review:
https://lore.kernel.org/qemu-devel/[email protected]/T/
[5] v11 review:
https://lore.kernel.org/qemu-devel/[email protected]/T/
fanhuang (4):
hw/mem: add sp-mem device for Specific Purpose Memory
i386/acpi-build: partition device_memory SRAT umbrella for sp-mem
hw/i386: hook sp-mem into the pc machine plug path
MAINTAINERS: cover sp-mem under Memory devices, add R: tag
MAINTAINERS | 3 +
qapi/machine.json | 43 ++++++++++-
hw/i386/e820_memory_layout.h | 11 +--
include/hw/mem/sp-mem.h | 33 +++++++++
hw/core/machine-hmp-cmds.c | 11 +++
hw/i386/acpi-build.c | 96 +++++++++++++++++++++++--
hw/i386/pc.c | 36 ++++++++++
hw/mem/sp-mem.c | 136 +++++++++++++++++++++++++++++++++++
hw/i386/Kconfig | 2 +
hw/mem/Kconfig | 4 ++
hw/mem/meson.build | 1 +
11 files changed, 365 insertions(+), 11 deletions(-)
create mode 100644 include/hw/mem/sp-mem.h
create mode 100644 hw/mem/sp-mem.c
base-commit: 2f28d34ea0aead9830478cd1d3d0dd9d9191d82e
--
2.34.1
