10277 broke older Intel CPUs
The changes in 10277 were not quite correct and on older Intel CPUs without CPUID leaf 0xb, such systems fail to boot. The problem is that the logic in cpuid_intel_ncores() is incorrect. While we correctly source the number of cores via leaf 4, we incorrectly assigned the number of threads based on the number sharing the smallest cache. This is basically never correct.
Instead, this needs to be obtained the same way it was in the past, via cpuid leaf 1.
Updated by Electric Monk about 2 years ago
- Status changed from New to Closed
commit d6517bbd3d5d20a36c32ac87627207632e5934aa Author: Robert Mustacchi <email@example.com> Date: 2019-03-12T15:31:31.000Z 10514 10277 broke older Intel CPUs 10513 Regression in westmere MCA initialization Reviewed by: Jerry Jelinek <firstname.lastname@example.org> Reviewed by: John Levon <email@example.com> Reviewed by: Peter Tribble <firstname.lastname@example.org> Approved by: Dan McDonald <email@example.com>