Fix Attention Mask Padding to Ensure Multiple of 8 Alignment

[SahilCarterr]

What does this PR do?

Fixes #9637 resolve Attention Mask Padding Issue for Compatibility with xFormers

Before submitting

• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• [x] Did you write any new necessary tests?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. @sayakpaul @yiyixuxu

---

Code from Issue

from diffusers.models.attention_processor import Attention, XFormersAttnProcessor
import torch

# Initialize the attention processor
attn_processer = XFormersAttnProcessor()

# Create the Attention module
attn = Attention(
    query_dim=256,
    heads=8,
    dim_head=64,
    processor=attn_processer,
).to(device="cuda", dtype=torch.bfloat16)

# Create dummy inputs
q = torch.zeros((2, 350, 256), device="cuda", dtype=torch.bfloat16)
kv = torch.zeros((2, 700, 256), device="cuda", dtype=torch.bfloat16)
attn_mask = torch.zeros((2, 1, 700), device="cuda", dtype=torch.bfloat16)

# Perform the attention operation
out = attn(q, kv, attn_mask)

# Print the output shape
print(out.shape)

Output

torch.Size([2, 350, 256])

Hardware Information

• GPU: NVIDIA A100
• Environment: Google Colab

[HuggingFaceDocBuilderDev]

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[SahilCarterr]

can you help to fix this error when i run the test script RuntimeError: expand(CUDABFloat16Type{[16, 1, 1, 278]}, size=[16, 1, 278]): the number of sizes provided (3) must be greater or equal to the number of dimensions in the tensor (4) . @sayakpaul . i have updated the test