Describe the bug

Description:
When running evaluation using the Intel Extension for PyTorch (IPEX) transformers.models.reference implementation of PhiModel, the forward pass fails because the _use_flash_attention_2 attribute is not defined in the model, but it is referenced in PhiModel_forward.

Transformers version used: 4.48.0

This seems to be caused by upstream Hugging Face transformers changes that introduced the _use_flash_attention_2 flag, but the IPEX PhiModel implementation does not initialize it in its constructor.

Suggested Fix / Monkey patch:
File: https://github.com/intel/intel-extension-for-pytorch/blob/main/intel_extension_for_pytorch/transformers/models/reference/models.py
Add this before checking if self._use_flash_attention_2:

if not hasattr(self, "_use_flash_attention_2"):
self._use_flash_attention_2 = False

Versions

Collecting environment information...

PyTorch version: 2.8.0+cpu
PyTorch CXX11 ABI: Yes
IPEX version: 2.8.0+cpu
IPEX commit: d87d51c
Build type: Release

OS: Ubuntu 22.04 LTS (x86_64)
GCC version: (Ubuntu 13.1.0-8ubuntu1~22.04) 13.1.0
Clang version: 14.0.0-1ubuntu1.1
IGC version: N/A
CMake version: version 3.22.1
Libc version: glibc-2.35

Python version: 3.10.18 | packaged by conda-forge | (main, Jun 4 2025, 14:45:41) [GCC 13.3.0] (64-bit runtime)
Python platform: Linux-5.15.0-131-generic-x86_64-with-glibc2.35
Is XPU available: False
DPCPP runtime: N/A
MKL version: N/A

GPU models and configuration onboard:
N/A

GPU models and configuration detected:
N/A

Driver version:

• intel_opencl: N/A
• level_zero: N/A

CPU:
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Address sizes: 52 bits physical, 57 bits virtual
Byte Order: Little Endian
CPU(s): 192
On-line CPU(s) list: 0-95
Off-line CPU(s) list: 96-191
Vendor ID: AuthenticAMD
Model name: AMD EPYC 9454 48-Core Processor
CPU family: 25
Model: 17
Thread(s) per core: 1
Core(s) per socket: 48
Socket(s): 2
Stepping: 1
BogoMIPS: 5500.11
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 cdp_l3 invpcid_single hw_pstate ssbd mba ibrs ibpb stibp ibrs_enhanced vmmcall fsgsbase bmi1 avx2 smep bmi2 erms invpcid cqm rdt_a avx512f avx512dq rdseed adx smap avx512ifma clflushopt clwb avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local avx512_bf16 clzero irperf xsaveerptr rdpru wbnoinvd amd_ppin cppc arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif v_spec_ctrl avx512vbmi umip pku ospke avx512_vbmi2 gfni vaes vpclmulqdq avx512_vnni avx512_bitalg avx512_vpopcntdq la57 rdpid overflow_recov succor smca fsrm flush_l1d
Virtualization: AMD-V
L1d cache: 3 MiB (96 instances)
L1i cache: 3 MiB (96 instances)
L2 cache: 96 MiB (96 instances)
L3 cache: 512 MiB (16 instances)
NUMA node(s): 2
NUMA node0 CPU(s): 0-47
NUMA node1 CPU(s): 48-95
Vulnerability Gather data sampling: Not affected
Vulnerability Itlb multihit: Not affected
Vulnerability L1tf: Not affected
Vulnerability Mds: Not affected
Vulnerability Meltdown: Not affected
Vulnerability Mmio stale data: Not affected
Vulnerability Reg file data sampling: Not affected
Vulnerability Retbleed: Not affected
Vulnerability Spec rstack overflow: Mitigation; safe RET
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp
Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2: Mitigation; Enhanced / Automatic IBRS; IBPB conditional; STIBP always-on; RSB filling; PBRSB-eIBRS Not affected; BHI Not affected
Vulnerability Srbds: Not affected
Vulnerability Tsx async abort: Not affected

Versions of relevant libraries:
[conda] intel-extension-for-pytorch 2.8.0 pypi_0 pypi
[conda] numpy 2.1.2 pypi_0 pypi
[conda] torch 2.8.0+cpu pypi_0 pypi
[conda] torchaudio 2.8.0+cpu pypi_0 pypi
[conda] torchinfo 1.8.0 pypi_0 pypi
[conda] torchvision 0.23.0+cpu pypi_0 pypi
[conda] transformers 4.48.0 pypi_0 pypi
[conda] transformers-stream-generator 0.0.5 pypi_0 pypi