summaryrefslogtreecommitdiff
path: root/arch
diff options
context:
space:
mode:
authorThomas Gleixner <tglx@linutronix.de>2024-03-22 19:56:38 +0100
committerBorislav Petkov (AMD) <bp@alien8.de>2024-03-23 12:35:56 +0100
commit5e25eb25dae9fa0700bbe42aff0e2f105fcd096a (patch)
tree6a1a5f5c2bc342f86bcf8e42e560229ca90532c5 /arch
parent7af541cee1e0eb48c6eb439bc6309175339fa96f (diff)
x86/topology: Handle the !APIC case gracefully
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: f1f758a80516 ("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
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/topology.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index 3259b1d4fefe..aaca8d235dc2 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -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;