On Thu, 2 May 2024 at 14:50, Marcin Juszkiewicz <marcin.juszkiew...@linaro.org> wrote: > Both hw/arm/sbsa-ref.c and hw/arm/virt.c build cpu information in > DeviceTree using "arm_build_mp_afinnity()" function. So if firmware > parses it then it gets wrong values.
What wrong values? The values in the dtb should match the Aff* fields, they are not the complete MPIDR_EL1 values including U and MT bits and so on: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/arm/cpus.yaml#n42 AIUI the ACPI spec says the same. > Firmware should probably read MPIDR_EL1 directly instead but what with > those who read DT and rely on this value already? Firmware should probably not read MPIDR_EL1 directly for topology information, because it's too vague and unreliable. Either it's real-hardware firmware, in which case it presumably knows the topology already, or else it's running on QEMU, in which case this is one of the things we can feed it via the DTB (either on virt or or sbsa-ref). thanks -- PMM
