Unified-shared memory (SVM) unsupported by GIM — XNACK not supported for MI210

[tob2]

The following seems to be an important missing feature — and is (until fixed) a documentation issue as well.

Using GIM, with an MI210 shows — even with HSA_XNACK=1:

# HSA_XNACK=1 rocminfo | grep xnack
Name:                    amdgcn-amd-amdhsa--gfx90a:sramecc+:xnack-

note the '–' after xnack. Querying ROCm via the API functions yields the same result:

HSA_AMD_SYSTEM_INFO_SVM_SUPPORTED = 1
HSA_AMD_SYSTEM_INFO_SVM_ACCESSIBLE_BY_DEFAULT = 0
HSA_AMD_SYSTEM_INFO_XNACK_ENABLED = 0

Without GIM, the result for the latter two is 1.

NOTE: I have not tried an MI300A – because the MI300A, I have access to, doesn't use GIM; hence, no idea whether it has the very same issue or whether it works there.

EXPECTED:

• Add soon to the documentation that Unified-Shared Memory / SVM accessibility / XNACK is not supported
• Actually add support for it (and then remove that entry again).

[yunxiali]

Thank you for bringing this to our attention. XNACK is currently unavailable on MI210 under SR-IOV. We will update the relevant ROCm documentation to clarify this behavior. Support for XNACK under SR-IOV is available starting with the MI300 series and newer accelerators.