Hi Alistair, On Mon, 6 Jul 2026 14:08:45 +1000, Alistair Francis wrote: > What happens to kernels that don't have this change?
Good question. The behavior depends on how old the kernel is: - Kernels that support _DEP processing but lack the acpi_dev_clear_dependencies() call in acpi_pci_root_add(): the ACPI0017 (CXLM) device will remain deferred indefinitely because its declared dependency on ACPI0016 is never cleared. CXL memory would be unusable on such kernels with this QEMU. - Very old kernels that ignore _DEP entirely: the behavior is the same as v1 ??? the probe-ordering race between acpi_pci_root and cxl_acpi remains, but nothing is worse than before. The kernel-side fix has already merged: https://lore.kernel.org/linux-pci/[email protected]/ So this is effectively a "new QEMU requires a sufficiently new kernel for CXL to work" situation, similar to other QEMU features that depend on kernel support. Thanks, Pei
