[Bugfix] Temporarily disable gptq_bitblas on ROCm

[nlzy]

In v0.8.5, those lines of code replaces gptq with gptq_bitblas:

vllm/vllm/config.py

Lines 795 to 810 in ba41cc9

	quantization_override = method.override_quantization_method(
	quant_cfg, self.quantization)
	if quantization_override is not None:
	# Raise error if the override is not custom (custom would
	# be in QUANTIZATION_METHODS but not QuantizationMethods)
	# and hasn't been added to the overrides list.
	if (name in get_args(QuantizationMethods)
	and name not in overrides):
	raise ValueError(
	f"Quantization method {name} is an override but "
	"is has not been added to the `overrides` list "
	"above. This is necessary to ensure that the "
	"overrides are checked in order of preference.")
	quant_method = quantization_override
	self.quantization = quantization_override
	break

After the replacement, a check is introduced to verify whether the current platform supports the specified quantization method:

vllm/vllm/config.py

Line 828 in ba41cc9

current_platform.verify_quantization(self.quantization)

However, gptq_bitblas is not included in the list of supported methods for ROCm, causing vLLM to throw an exception and exit:

vllm/vllm/platforms/rocm.py

Lines 132 to 135 in ba41cc9

	supported_quantization: list[str] = [
	"awq", "gptq", "fp8", "compressed-tensors", "fbgemm_fp8", "gguf",
	"quark", "ptpc_fp8"
	]

Due to this check, gptq_bitblas should not be functional on the ROCm platform in this version of vLLM. Any user attempting to use gptq_bitblas on ROCm should encounter this error and the program will exit.

In other words, it appears that no one has actually tested or successfully run gptq_bitblas on the ROCm platform. In this situation, I believe we should temporarily disable gptq_bitblas for ROCm users. The feature can be re-enabled once a developer successfully tests and runs gptq_bitblas on ROCm.

This PR primarily considers users on the ROCm platform who rely on GPTQ quantization. These users will encounter issues where vLLM fails to start after updating from v0.8.4 to v0.8.5.

FIX #17410

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[mgoin]

cc @LeiWang1999 this seems reasonable, is this okay with you?

[LeiWang1999]

Sorry for the trouble, lgtm. currently BitBLAS support for ROCm requires building from source. We will submit another PR to enable the ROCm backend once our ROCm solution is ready.