History log of /linux-master/arch/x86/kernel/cpu/topology_ext.c
Revision Date Author Comments
# 3d410094 13-Feb-2024 Thomas Gleixner <tglx@linutronix.de>

x86/cpu: Provide a sane leaf 0xb/0x1f parser

detect_extended_topology() along with it's early() variant is a classic
example for duct tape engineering:

- It evaluates an array of subleafs with a boatload of local variables
for the relevant topology levels instead of using an array to save the
enumerated information and propagate it to the right level

- It has no boundary checks for subleafs

- It prevents updating the die_id with a crude workaround instead of
checking for leaf 0xb which does not provide die information.

- It's broken vs. the number of dies evaluation as it uses:

num_processors[DIE_LEVEL] / num_processors[CORE_LEVEL]

which "works" only correctly if there is none of the intermediate
topology levels (MODULE/TILE) enumerated.

There is zero value in trying to "fix" that code as the only proper fix is
to rewrite it from scratch.

Implement a sane parser with proper code documentation, which will be used
for the consolidated topology evaluation in the next step.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juergen Gross <jgross@suse.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Tested-by: Wang Wendy <wendy.wang@intel.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lore.kernel.org/r/20240212153624.830571770@linutronix.de