[GSD-13095] SYCL global_mem_size reports PF total LMEM instead of VF partition on some SR-IOV VFs (Arc Pro B70)

[abyrne55]

Pre-submission Checklist

• I am using the latest GPU driver version (releases)
• I have searched for similar issues and found none

GPU Hardware

Intel Arc Pro B70 (BMG-G31, PCI ID 8086:e223)

DRI Devices Information

2x Arc Pro B70 PFs with 4 SR-IOV VFs each (8 VFs total):

$ ls -la /dev/dri/by-path/
pci-0000:18:00.0-card -> ../card1      # GPU1 PF
pci-0000:18:00.0-render -> ../renderD128
pci-0000:18:00.1-card -> ../card3      # GPU1 VF1
pci-0000:18:00.1-render -> ../renderD130
pci-0000:18:00.2-card -> ../card4      # GPU1 VF2
pci-0000:18:00.2-render -> ../renderD131
pci-0000:18:00.3-card -> ../card5      # GPU1 VF3
pci-0000:18:00.3-render -> ../renderD132
pci-0000:18:00.4-card -> ../card6      # GPU1 VF4
pci-0000:18:00.4-render -> ../renderD133
pci-0000:54:00.0-card -> ../card2      # GPU2 PF
pci-0000:54:00.0-render -> ../renderD129
pci-0000:54:00.1-card -> ../card7      # GPU2 VF1
pci-0000:54:00.1-render -> ../renderD134
pci-0000:54:00.2-card -> ../card8      # GPU2 VF2
pci-0000:54:00.2-render -> ../renderD135
pci-0000:54:00.3-card -> ../card9      # GPU2 VF3
pci-0000:54:00.3-render -> ../renderD136
pci-0000:54:00.4-card -> ../card10     # GPU2 VF4
pci-0000:54:00.4-render -> ../renderD137

GPU Detailed Information (lspci output)

18:00.0 VGA compatible controller: Intel Corporation Battlemage G31 [Intel Graphics] (prog-if 00 [VGA controller])
	Subsystem: Intel Corporation Device 1701
	Region 0: Memory at 207804000000 (64-bit, prefetchable) [size=16M]
	Region 2: Memory at 206800000000 (64-bit, prefetchable) [size=32G]
	Capabilities: [420 v1] Physical Resizable BAR
		BAR 2: current size: 32GB, supported: 256MB 512MB 1GB 2GB 4GB 8GB 16GB 32GB
	Capabilities: [220 v1] Virtual Resizable BAR
		BAR 2: current size: 8GB, supported: 256MB 512MB 1GB 2GB 4GB 8GB 16GB 32GB
	Capabilities: [320 v1] Single Root I/O Virtualization (SR-IOV)
		IOVCap:	Migration-, Interrupt Message Number: 000
		IOVCtl:	Enable+ Migration- Interrupt- MSE+ ARIHierarchy+
		Initial VFs: 4, Total VFs: 4, Number of VFs: 4, Function Dependency Link: 00
		VF offset: 1, stride: 1, Device ID: e223
	Kernel driver in use: xe

All VF BAR2 sizes are identical at 8 GiB (stat -c %s /sys/bus/pci/devices/0000:XX:00.Y/resource2 = 8589934592 for all VFs).

Driver Version

26.18.38308.4

Installed GPU Driver Packages

Tested inside docker.io/intel/oneapi:2026.0.0-devel-rockylinux10 container with packages upgraded to latest:

intel-compute-runtime-26.18.38308.4-1.el10_2.x86_64
intel-level-zero-26.18.38308.4-1.el10_2.x86_64
intel-igc-2.34.4-4.el10_2.x86_64
intel-igc-libs-2.34.4-4.el10_2.x86_64
intel-gmmlib-22.8.1-2.el10_1.x86_64
intel-opencl-26.18.38308.4-1.el10_2.x86_64
intel-ocloc-26.18.38308.4-1.el10_2.x86_64

Driver Installation Details

Packages installed from the Rocky Linux 10 Intel GPU repos (dnf upgrade intel-level-zero intel-compute-runtime intel-igc intel-igc-libs intel-opencl intel-ocloc oneapi-level-zero). Workloads run as Kubernetes pods with DRA-assigned /dev/dri/renderD* devices (one VF per pod).

Linux Distribution

Fedora / RHEL

Other Linux Distribution

RHEL CoreOS 9.8 (OpenShift 4.22.2). Userspace runs inside Rocky Linux 10 containers.

Kernel Version & Boot Parameters

$ uname -r
5.14.0-687.15.1.el9_8.x86_64

$ cat /proc/cmdline
... pci=realloc intel_iommu=on iommu=pt ...

$ lsmod | grep xe
xe                   3985408  4

Actual Behavior

sycl::info::device::global_mem_size reports the full PF LMEM size (~31023 MiB) on some SR-IOV VFs instead of the correct per-VF partition (~7719 MiB). Affected VFs vary per GPU — on this system, GPU1 VF1 and VF4 are affected while GPU1 VF2-3 and all GPU2 VFs report correctly.

Tested by deploying one SYCL pod per VF (PCI-address-pinned via DRA ResourceClaims), each running:

auto dev = q.get_device();
std::cout << "Memory: " << dev.get_info<sycl::info::device::global_mem_size>() / (1024*1024) << " MiB" << std::endl;

Results:

VF	PCI Address	SYCL global_mem_size	Expected
GPU1 VF1	0000:18:00.1	31023 MiB	7719 MiB
GPU1 VF2	0000:18:00.2	7719 MiB	7719 MiB
GPU1 VF3	0000:18:00.3	7719 MiB	7719 MiB
GPU1 VF4	0000:18:00.4	31023 MiB	7719 MiB
GPU2 VF1	0000:54:00.1	7719 MiB	7719 MiB
GPU2 VF2	0000:54:00.2	7719 MiB	7719 MiB
GPU2 VF3	0000:54:00.3	7719 MiB	7719 MiB
GPU2 VF4	0000:54:00.4	7719 MiB	7719 MiB

The values 7719 and 31023 are consistent with a 0.95 headroom factor applied to the correct VF size (8126 MiB) and the PF visible size (32656 MiB), respectively: 8126 * 0.95 ≈ 7719, 32656 * 0.95 ≈ 31023.

The kernel is not the source. The xe driver's TTM resource manager reports the correct size for all VFs, confirmed via debugfs:

# cat /sys/kernel/debug/dri/{card}/vram0_mm | grep 'man size'
card1  (0000:18:00.0) [PF]: man size:34242297856   (32656 MiB)
card3  (0000:18:00.1) [VF]: man size:8520728576    (8126 MiB)  <-- correct
card4  (0000:18:00.2) [VF]: man size:8520728576    (8126 MiB)
card5  (0000:18:00.3) [VF]: man size:8520728576    (8126 MiB)
card6  (0000:18:00.4) [VF]: man size:8520728576    (8126 MiB)  <-- correct
card7  (0000:54:00.1) [VF]: man size:8520728576    (8126 MiB)
...all VFs identical...

The DRM_IOCTL_XE_DEVICE_QUERY (MEM_REGIONS) response from the kernel is correct for all VFs. The misreporting happens in the compute-runtime/L0 userspace layer.

dmesg also confirms correct VF LMEM provisioning by the PF:

xe 0000:18:00.0: [drm] Tile0: GT0: PF: VF1..VF4 provisioned with 8520728576 (7.94 GiB) LMEM
xe 0000:54:00.0: [drm] Tile0: GT0: PF: VF1..VF4 provisioned with 8520728576 (7.94 GiB) LMEM

Expected Behavior

sycl::info::device::global_mem_size should report the VF's actual LMEM partition (~7719 MiB after headroom) on all VFs, matching the kernel-reported man->size of 8520728576 bytes.

Reproduction Rate

Always reproduces - 100%

Steps to Reproduce

1. System with 2x Intel Arc Pro B70 GPUs, xe driver loaded
2. Create 4 SR-IOV VFs per GPU: echo 4 > /sys/bus/pci/devices/0000:XX:00.0/sriov_numvfs
3. Run a SYCL program that queries sycl::info::device::global_mem_size on each VF independently (one process per VF, each seeing only its own /dev/dri/renderD*)
4. Compare reported memory across VFs — some report ~31023 MiB (PF value) instead of ~7719 MiB (VF value)

oneAPI Version (if applicable)

$ icpx --version
Intel(R) oneAPI DPC++/C++ Compiler 2026.0.0 (2026.0.0.20260331)
Target: x86_64-unknown-linux-gnu

Additional Notes

• Compute performance is not affected — all VFs deliver identical GFLOPS regardless of the reported memory value. The actual LMEM allocation and compute work correctly; only the reporting is wrong.
• vLLM inference also works correctly on affected VFs — Free memory on device (7.03/7.54 GiB) is reported accurately by the vLLM memory profiler path, which uses torch.xpu.mem_get_info() rather than global_mem_size.
• The pattern of which VFs are affected is not consistent with a "first VF" or "last VF" rule — it's VF1 + VF4 on GPU1 only, while GPU2 is unaffected.