mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-09-25 11:55:37 +00:00
Code Issues Releases Wiki Activity

x86/topology: Handle the !APIC case gracefully

Browse source 
If there is no local APIC enumerated and registered then the topology
bitmaps are empty. Therefore, topology_init_possible_cpus() will die with
a division by zero exception.

Prevent this by registering a fake APIC id to populate the topology
bitmap. This also allows to use all topology query interfaces
unconditionally. It does not affect the actual APIC code because either
the local APIC address was not registered or no local APIC could be
detected.

Fixes: f1f758a805 ("x86/topology: Add a mechanism to track topology via APIC IDs")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240322185305.242709302@linutronix.de
This commit is contained in:
Thomas Gleixner 2024-03-22 19:56:38 +01:00 committed by Borislav Petkov (AMD)
parent 7af541cee1
commit 5e25eb25da
1 changed files with 11 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

11
arch/x86/kernel/cpu/topology.c
View file

@ -415,6 +415,17 @@ void __init topology_init_possible_cpus(void)
unsigned int total = assigned + disabled;
u32 apicid, firstid;
/*
* If there was no APIC registered, then fake one so that the
* topology bitmap is populated. That ensures that the code below
* is valid and the various query interfaces can be used
* unconditionally. This does not affect the actual APIC code in
* any way because either the local APIC address has not been
* registered or the local APIC was disabled on the command line.
*/
if (topo_info.boot_cpu_apic_id == BAD_APICID)
topology_register_boot_apic(0);
if (!restrict_to_up()) {
if (WARN_ON_ONCE(assigned > nr_cpu_ids)) {
disabled += assigned - nr_cpu_ids;