x86/idt: Keep spurious entries unset in system_vectors

With commit dc20b2d52653 ("x86/idt: Move interrupt gate initialization to
IDT code") non assigned system vectors are also marked as used in
'used_vectors' (now 'system_vectors') bitmap. This makes checks in
arch_show_interrupts() whether a particular system vector is allocated to
always pass and e.g. 'Hyper-V reenlightenment interrupts' entry always
shows up in /proc/interrupts.

Another side effect of having all unassigned system vectors marked as used
is that irq_matrix_debug_show() will wrongly count them among 'System'
vectors.

As it is now ensured that alloc_intr_gate() is not called after init, it is
possible to leave unused entries in 'system_vectors' unset to fix these
issues.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200428093824.1451532-4-vkuznets@redhat.com

diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index 0e9205137de8a8638be97940a652051dcec240d8..36fef90a38e796b8e67b6658d39b8f0cc1f07bee 100644 (file)
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -321,7 +321,11 @@ void __init idt_setup_apic_and_irq_gates(void)
 
 #ifdef CONFIG_X86_LOCAL_APIC
        for_each_clear_bit_from(i, system_vectors, NR_VECTORS) {
-               set_bit(i, system_vectors);
+               /*
+                * Don't set the non assigned system vectors in the
+                * system_vectors bitmap. Otherwise they show up in
+                * /proc/interrupts.
+                */
                entry = spurious_entries_start + 8 * (i - FIRST_SYSTEM_VECTOR);
                set_intr_gate(i, entry);
        }