[Bugfix] Fix mc2 operator error in aclgraph + ep<16 scenario

[MengqingCao]

What this PR does / why we need it?

1. quickfix mc2 operator error in aclgraph + ep<16 scenario to recover CI, will be refactorred in the future
2. disable aclgraph when testing w8a8

How was this patch tested?

CI passed with existing test.

• vLLM version: v0.10.1.1
• vLLM main: vllm-project/vllm@9508960

[github-actions]

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[gemini-code-assist]

Code Review

This pull request introduces a quickfix for an mc2 operator error that occurs with aclgraph when the expert parallel size is less than 16. The fix involves forcing the allgathercommimpl communication method in this scenario. Additionally, aclgraph is disabled for w8a8 tests. My review focuses on making the main fix more precise to avoid potential performance regressions on hardware not affected by the bug.

[gemini-code-assist]

The added comment on line 244 states this limitation is specific to A3 hardware. However, this condition applies the restriction unconditionally, which could cause performance regressions on other hardware like A2. To align with the comment and make the fix more targeted, consider making the condition hardware-specific by checking the is_ascend_a3 flag from the mc2commimpl instance.

Suggested change

	if self.moe_config.ep_size < 16 and moe_comm_method_name != "dummycommimpl":
	if self.mc2commimpl.is_ascend_a3 and self.moe_config.ep_size < 16 and moe_comm_method_name != "dummycommimpl":

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 72.40%. Comparing base (dfc7eb3) to head (018ba13).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
vllm_ascend/ops/common_fused_moe.py	0.00%	1 Missing ⚠️

❌ Your patch status has failed because the patch coverage (0.00%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2609   +/-   ##
=======================================
  Coverage   72.40%   72.40%           
=======================================
  Files         146      146           
  Lines       21598    21598           
=======================================
  Hits        15639    15639           
  Misses       5959     5959           

Flag	Coverage Δ
unittests	72.40% <0.00%> (ø)

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[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[MengqingCao]

all the CI passed, plz help merge this to recover CI cc @Yikun @wangxiyuan