[PATCH AUTOSEL 4.19 170/172] x86/idt: Keep spurious entries unset in system_vectors

Sasha Levin
2020-06-18T01:54:43Z

From: Vitaly Kuznetsov <vkuznets@redhat.com>

[ Upstream commit 1f1fbc70c10e81f70e9fbe2102d439c883269811 ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kernel/idt.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index a7e0e975043f..e1f9355307b8 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -320,7 +320,11 @@ 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);
}
--
2.25.1