[ROCm] Derive device capability from GCN arch string without CUDA init (#35069)

Signed-off-by: Andreas Karatzas <akaratza@amd.com>

vllm/platforms/rocm.py

@@ -6,6 +6,7 @@ from datetime import timedelta
 from functools import cache, lru_cache, wraps
 from typing import TYPE_CHECKING
 
+import regex as re
 import torch
 from torch.distributed import PrefixStore, ProcessGroup
 from torch.distributed.distributed_c10d import is_nccl_available
@@ -64,13 +65,29 @@ _ROCM_DEVICE_ID_NAME_MAP: dict[str, str] = {
     "0x744c": "AMD_Radeon_RX7900XTX",
 }
 
-# Prevent use of clashing `{CUDA/HIP}_VISIBLE_DEVICES`
-if "HIP_VISIBLE_DEVICES" in os.environ:
-    val = os.environ["HIP_VISIBLE_DEVICES"]
-    if cuda_val := os.environ.get("CUDA_VISIBLE_DEVICES", None):
-        assert val == cuda_val
-    else:
-        os.environ["CUDA_VISIBLE_DEVICES"] = val
+
+def _sync_hip_cuda_env_vars():
+    """Ensure HIP_VISIBLE_DEVICES and CUDA_VISIBLE_DEVICES are consistent.
+    Treats empty string as unset. Raises on genuine conflicts."""
+    hip_val = os.environ.get("HIP_VISIBLE_DEVICES") or None
+    cuda_val = os.environ.get("CUDA_VISIBLE_DEVICES") or None
+
+    if hip_val is not None and cuda_val is not None:
+        if hip_val != cuda_val:
+            raise ValueError(
+                f"Inconsistent GPU visibility env vars: "
+                f"HIP_VISIBLE_DEVICES='{hip_val}' vs "
+                f"CUDA_VISIBLE_DEVICES='{cuda_val}'. "
+                f"Please set only one, or ensure they match."
+            )
+    elif hip_val is not None:
+        os.environ["CUDA_VISIBLE_DEVICES"] = hip_val
+    elif cuda_val is not None:
+        os.environ["HIP_VISIBLE_DEVICES"] = cuda_val
+
+
+# Sync at import time - catches misconfigurations from process start.
+_sync_hip_cuda_env_vars()
 
 # AMDSMI utils
 # Note that NVML is not affected by `{CUDA/HIP}_VISIBLE_DEVICES`,
@@ -134,6 +151,77 @@ _ON_GFX942 = "gfx942" in _GCN_ARCH
 _ON_GFX950 = "gfx950" in _GCN_ARCH
 
 
+def _capability_from_gcn_arch(gcn_arch: str) -> tuple[int, int] | None:
+    """
+    Parse (major, minor) from a GCN arch string, mirroring how
+    HIP derives hipDeviceProp_t.major / .minor.
+
+    Format: gfx<MAJOR><MINOR><STEPPING>
+      - 1-digit major  (gfx9xx):  "gfx" + M + m + stepping
+      - 2-digit major  (gfx1xxx): "gfx" + MM + m + stepping
+
+    Examples:
+      gfx90a  -> (9, 0)    gfx942  -> (9, 4)    gfx950 -> (9, 5)
+      gfx1100 -> (11, 0)   gfx1101 -> (11, 0)   gfx1200 -> (12, 0)
+
+    Returns None only when the string is not gfx-prefixed at all
+    (i.e. not a ROCm arch string). Raises on any string that looks
+    like a GCN arch but does not match a known layout.
+    """
+    m = re.match(r"gfx(\d+)", gcn_arch)
+    if not m:
+        # Not a gfx string at all — caller should fall back to torch.cuda
+        return None
+
+    digits = m.group(1)
+    n = len(digits)
+
+    if n < 2:
+        raise ValueError(
+            f"GCN arch '{gcn_arch}' has too few digits ({n}) after 'gfx' "
+            f"to derive a (major, minor) capability. "
+            f"Please file a vLLM issue with your GPU model."
+        )
+
+    if n in (2, 3):
+        # 1-digit major: gfx9 family
+        # len 2: major + minor          (e.g. gfx90 from gfx90a)
+        # len 3: major + minor + step   (e.g. gfx942)
+        major = int(digits[0])
+        minor = int(digits[1])
+    elif n == 4:
+        # 2-digit major: gfx10xx, gfx11xx, gfx12xx
+        # major(2) + minor(1) + stepping(1)
+        major = int(digits[:2])
+        minor = int(digits[2])
+    elif n >= 5:
+        raise ValueError(
+            f"GCN arch '{gcn_arch}' has {n} digits after 'gfx', which "
+            f"exceeds the known 4-digit layout (MMms). Cannot determine "
+            f"major/minor split unambiguously. "
+            f"Please file a vLLM issue with your GPU model."
+        )
+
+    if major < 9:
+        raise ValueError(
+            f"Parsed unknown ROCm architecture from GCN arch '{gcn_arch}': "
+            f"major={major}, minor={minor}. "
+            f"Major version < 9 is not expected for any supported AMD GPU. "
+            f"Please file a vLLM issue with your GPU model."
+        )
+
+    if major > 12:
+        raise ValueError(
+            f"Parsed unknown ROCm architecture from GCN arch '{gcn_arch}': "
+            f"major={major}, minor={minor}. "
+            f"Major version > 12 is beyond currently known AMD generations. "
+            f"Please file a vLLM issue with your GPU model so support "
+            f"can be added."
+        )
+
+    return (major, minor)
+
+
 def on_gfx1x() -> bool:
     return _ON_GFX1X
 
@@ -444,6 +532,15 @@ class RocmPlatform(Platform):
     @classmethod
     @lru_cache(maxsize=8)
     def get_device_capability(cls, device_id: int = 0) -> DeviceCapability | None:
+        cap = _capability_from_gcn_arch(_GCN_ARCH)
+        if cap is not None:
+            return DeviceCapability(major=cap[0], minor=cap[1])
+
+        logger.warning_once(
+            "Could not derive device capability from GCN arch '%s', "
+            "falling back to torch.cuda (this will initialize CUDA).",
+            _GCN_ARCH,
+        )
         major, minor = torch.cuda.get_device_capability(device_id)
         return DeviceCapability(major=major, minor=minor)
 

vllm/utils/system_utils.py

@@ -16,6 +16,7 @@ import psutil
 
 import vllm.envs as envs
 from vllm.logger import init_logger
+from vllm.platforms import current_platform
 from vllm.platforms.interface import in_wsl
 from vllm.ray.lazy_utils import is_in_ray_actor
 
@@ -111,6 +112,17 @@ def unique_filepath(fn: Callable[[int], Path]) -> Path:
 # Process management utilities
 
 
+def _sync_visible_devices_env_vars():
+    """Sync HIP/CUDA visibility env vars before spawning (ROCm only)."""
+
+    if not current_platform.is_rocm():
+        return
+
+    from vllm.platforms.rocm import _sync_hip_cuda_env_vars
+
+    _sync_hip_cuda_env_vars()
+
+
 def _maybe_force_spawn():
     """Check if we need to force the use of the `spawn` multiprocessing start
     method.
@@ -156,6 +168,10 @@ def get_mp_context():
     VLLM_WORKER_MULTIPROC_METHOD.
     """
     _maybe_force_spawn()
+    # (ROCm): Sync GPU visibility env vars so spawned children inherit
+    # consistent values. Must run after _maybe_force_spawn and regardless
+    # of whether spawn was already set.
+    _sync_visible_devices_env_vars()
     mp_method = envs.VLLM_WORKER_MULTIPROC_METHOD
     return multiprocessing.get_context(mp_method)