[PATCH] x86/ioapic: Disable interrupts when re-routing legacy IRQs

[PATCH] x86/ioapic: Disable interrupts when re-routing legacy IRQs

[Vitaly Kuznetsov]

A sporadic hang with consequent crash is observed when booting Hyper-V Gen1
guests:

 Call Trace:
  <IRQ>
  [<ffffffff810ab68d>] ? trace_hardirqs_off+0xd/0x10
  [<ffffffff8107b616>] queue_work_on+0x46/0x90
  [<ffffffff81365696>] ? add_interrupt_randomness+0x176/0x1d0
  ...
  <EOI>
  [<ffffffff81471ddb>] ? _raw_spin_unlock_irqrestore+0x3b/0x60
  [<ffffffff810c295e>] __irq_put_desc_unlock+0x1e/0x40
  [<ffffffff810c5c35>] irq_modify_status+0xb5/0xd0
  [<ffffffff8104adbb>] mp_register_handler+0x4b/0x70
  [<ffffffff8104c55a>] mp_irqdomain_alloc+0x1ea/0x2a0
  [<ffffffff810c7f10>] irq_domain_alloc_irqs_recursive+0x40/0xa0
  [<ffffffff810c860c>] __irq_domain_alloc_irqs+0x13c/0x2b0
  [<ffffffff8104b070>] alloc_isa_irq_from_domain.isra.1+0xc0/0xe0
  [<ffffffff8104bfa5>] mp_map_pin_to_irq+0x165/0x2d0
  [<ffffffff8104c157>] pin_2_irq+0x47/0x80
  [<ffffffff81744253>] setup_IO_APIC+0xfe/0x802
  ...
  [<ffffffff814631c0>] ? rest_init+0x140/0x140

The issue is easily reproducible with a simple instrumentation: if
mdelay(10) is put between mp_setup_entry() and mp_register_handler() calls
in mp_irqdomain_alloc() Hyper-V guest always fails to boot when re-routing
IRQ0. The issue seems to be caused by the fact that we don't disable
interrupts while doing IOPIC programming for legacy IRQs and IRQ0 actually
happens. Decorate manipulations with legacy IRQs with local_irq_save()/
local_irq_restore().

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
It may make sense to have interrupts disabled for non-legacy IRQs as well
but I'm unaware of any bugs with them at this moment.
---
 arch/x86/kernel/apic/io_apic.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 5c60bb1..9aac777 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2907,6 +2907,7 @@ int mp_irqdomain_alloc(struct irq_domain *domain, unsigned int virq,
 	struct irq_data *irq_data;
 	struct mp_chip_data *data;
 	struct irq_alloc_info *info = arg;
+	unsigned long flags = 0;
 
 	if (!info || nr_irqs > 1)
 		return -EINVAL;
@@ -2939,11 +2940,16 @@ int mp_irqdomain_alloc(struct irq_domain *domain, unsigned int virq,
 
 	cfg = irqd_cfg(irq_data);
 	add_pin_to_irq_node(data, ioapic_alloc_attr_node(info), ioapic, pin);
+
+	if (virq < nr_legacy_irqs())
+		local_irq_save(flags);
 	if (info->ioapic_entry)
 		mp_setup_entry(cfg, data, info->ioapic_entry);
 	mp_register_handler(virq, data->trigger);
-	if (virq < nr_legacy_irqs())
+	if (virq < nr_legacy_irqs()) {
 		legacy_pic->mask(virq);
+		local_irq_restore(flags);
+	}
 
 	apic_printk(APIC_VERBOSE, KERN_DEBUG
 		    "IOAPIC[%d]: Set routing entry (%d-%d -> 0x%x -> IRQ %d Mode:%i Active:%i Dest:%d)\n",
-- 
2.4.3

[tip:x86/urgent] x86/ioapic: Disable interrupts when re-routing legacy IRQs

[tip-bot for Vitaly Kuznetsov]

Commit-ID:  c0ff971ef9acacd4d2caa508e444edad958dead9
Gitweb:     http://git.kernel.org/tip/c0ff971ef9acacd4d2caa508e444edad958dead9
Author:     Vitaly Kuznetsov <vkuznets@redhat.com>
AuthorDate: Thu, 15 Oct 2015 19:42:23 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 16 Oct 2015 16:31:24 +0200

x86/ioapic: Disable interrupts when re-routing legacy IRQs

A sporadic hang with consequent crash is observed when booting Hyper-V Gen1
guests:

 Call Trace:
  <IRQ>
  [<ffffffff810ab68d>] ? trace_hardirqs_off+0xd/0x10
  [<ffffffff8107b616>] queue_work_on+0x46/0x90
  [<ffffffff81365696>] ? add_interrupt_randomness+0x176/0x1d0
  ...
  <EOI>
  [<ffffffff81471ddb>] ? _raw_spin_unlock_irqrestore+0x3b/0x60
  [<ffffffff810c295e>] __irq_put_desc_unlock+0x1e/0x40
  [<ffffffff810c5c35>] irq_modify_status+0xb5/0xd0
  [<ffffffff8104adbb>] mp_register_handler+0x4b/0x70
  [<ffffffff8104c55a>] mp_irqdomain_alloc+0x1ea/0x2a0
  [<ffffffff810c7f10>] irq_domain_alloc_irqs_recursive+0x40/0xa0
  [<ffffffff810c860c>] __irq_domain_alloc_irqs+0x13c/0x2b0
  [<ffffffff8104b070>] alloc_isa_irq_from_domain.isra.1+0xc0/0xe0
  [<ffffffff8104bfa5>] mp_map_pin_to_irq+0x165/0x2d0
  [<ffffffff8104c157>] pin_2_irq+0x47/0x80
  [<ffffffff81744253>] setup_IO_APIC+0xfe/0x802
  ...
  [<ffffffff814631c0>] ? rest_init+0x140/0x140

The issue is easily reproducible with a simple instrumentation: if
mdelay(10) is put between mp_setup_entry() and mp_register_handler() calls
in mp_irqdomain_alloc() Hyper-V guest always fails to boot when re-routing
IRQ0. The issue seems to be caused by the fact that we don't disable
interrupts while doing IOPIC programming for legacy IRQs and IRQ0 actually
happens. 

Protect the setup sequence against concurrent interrupts.

[ tglx: Make the protection unconditional and not only for legacy
  	interrupts ]

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Link: http://lkml.kernel.org/r/1444930943-19336-1-git-send-email-vkuznets@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/apic/io_apic.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 5c60bb1..bb6bfc0 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2907,6 +2907,7 @@ int mp_irqdomain_alloc(struct irq_domain *domain, unsigned int virq,
 	struct irq_data *irq_data;
 	struct mp_chip_data *data;
 	struct irq_alloc_info *info = arg;
+	unsigned long flags;
 
 	if (!info || nr_irqs > 1)
 		return -EINVAL;
@@ -2939,11 +2940,14 @@ int mp_irqdomain_alloc(struct irq_domain *domain, unsigned int virq,
 
 	cfg = irqd_cfg(irq_data);
 	add_pin_to_irq_node(data, ioapic_alloc_attr_node(info), ioapic, pin);
+
+	local_irq_save(flags);
 	if (info->ioapic_entry)
 		mp_setup_entry(cfg, data, info->ioapic_entry);
 	mp_register_handler(virq, data->trigger);
 	if (virq < nr_legacy_irqs())
 		legacy_pic->mask(virq);
+	local_irq_restore(flags);
 
 	apic_printk(APIC_VERBOSE, KERN_DEBUG
 		    "IOAPIC[%d]: Set routing entry (%d-%d -> 0x%x -> IRQ %d Mode:%i Active:%i Dest:%d)\n",