On 1/5/2026 5:57 PM, Gerd Hoffmann wrote:
On Mon, Jan 05, 2026 at 03:25:06PM +0800, fanhuang wrote:
Add support for E820 Soft Reserved Memory regions in OVMF firmware.
This memory type is used by QEMU to expose Specific Purpose Memory (SPM).
Please open a PR at github for this.
Also: This needs more context. What is SPM? Where is this specified?
Are there corresponding patches for qemu? If so, where?
take care,
Gerd
Hi Gerd,
Thank you for your feedback. Let me provide more context:
What is SPM (Specific Purpose Memory)?
SPM is defined in ACPI 6.4+ specification (Section 15.3.3) as memory
intended for specific use cases like:
- High Bandwidth Memory (HBM) attached to accelerators/GPUs
- CXL memory devices
- Other heterogeneous memory
In E820 terms, SPM corresponds to the "Soft Reserved" memory type
(E820_TYPE_SOFT_RESERVED, type 0xefffffff), which indicates memory that:
- Should NOT be used by the OS for general allocation
- Can be managed by device drivers for specific purposes
- Is reported via ACPI SRAT/HMAT for NUMA awareness
Use Case: HBM Management
This feature supports AMD's A+A architecture where GPU HBM memory is
exposed to the guest VM:
1. QEMU marks the memory region with E820 Soft Reserved type
2. OVMF (this patch) recognizes it and creates appropriate HOBs
3. Linux kernel driver can then manage it as driver-controlled memory
QEMU Patches
The corresponding QEMU patches are under review on qemu-devel:
https://lore.kernel.org/qemu-devel/[email protected]/T/
The QEMU changes add a "spm=on" option to "-numa node" command line.
PR
I've opened a PR as you suggested:
https://github.com/tianocore/edk2/pull/11964
Best regards,
FangSheng Huang
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