[linux-yocto] [PATCH 4/6] genirq: x86: Ensure that dynamic irq allocation does not conflict

wan.ahmad.zainie.wan.mohamad at intel.com wan.ahmad.zainie.wan.mohamad at intel.com
Mon Nov 16 18:54:18 PST 2015

From: Thomas Gleixner <tglx at linutronix.de>

On x86 the allocation of irq descriptors may allocate interrupts which
are in the range of the GSI interrupts. That's wrong as those
interrupts are hardwired and we don't have the irq domain translation
like PPC. So one of these interrupts can be hooked up later to one of
the devices which are hard wired to it and the io_apic init code for
that particular interrupt line happily reuses that descriptor with a
completely different configuration so hell breaks lose.

Inside x86 we allocate dynamic interrupts from above nr_gsi_irqs,
except for a few usage sites which have not yet blown up in our face
for whatever reason. But for drivers which need an irq range, like the
GPIO drivers, we have no limit in place and we don't want to expose
such a detail to a driver.

To cure this introduce a function which an architecture can implement
to impose a lower bound on the dynamic interrupt allocations.

Implement it for x86 and set the lower bound to nr_gsi_irqs, which is
the end of the hardwired interrupt space, so all dynamic allocations
happen above.

That not only allows the GPIO driver to work sanely, it also protects
the bogus callsites of create_irq_nr() in hpet, uv, irq_remapping and
htirq code. They need to be cleaned up as well, but that's a separate

Refer to HSD4995193.

Reported-by: Jin Yao <yao.jin at linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Tested-by: Mika Westerberg <mika.westerberg at linux.intel.com>
Cc: Mathias Nyman <mathias.nyman at linux.intel.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Grant Likely <grant.likely at linaro.org>
Cc: H. Peter Anvin <hpa at linux.intel.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Cc: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
Cc: Krogerus Heikki <heikki.krogerus at intel.com>
Cc: Linus Walleij <linus.walleij at linaro.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1404241617360.28206@ionos.tec.linutronix.de
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
(cherry picked from commit 62a08ae2a5763aabeee98264605236b001503e0c)



	Manually edited the original patch to make it apply smoothly.

Signed-off-by: Maurice Petallo <mauricex.r.petallo at intel.com>
Change-Id: I7ff269d69af1546db0370bed7edf81bf8dc9ed11
Reviewed-on: https://git-gar-1.devtools.intel.com/gerrit/5707
Reviewed-by: Wan Mohamad, Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad at intel.com>
Reviewed-by: Tan, Jui Nee <jui.nee.tan at intel.com>
 arch/x86/kernel/apic/io_apic.c | 5 +++++
 include/linux/irq.h            | 2 ++
 kernel/irq/irqdesc.c           | 7 +++++++
 kernel/softirq.c               | 5 +++++
 4 files changed, 19 insertions(+)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 9ed796c..f5f67f9 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3420,6 +3420,11 @@ int get_nr_irqs_gsi(void)
 	return nr_irqs_gsi;
+unsigned int arch_dynirq_lower_bound(unsigned int from)
+	return from < nr_irqs_gsi ? nr_irqs_gsi : from;
 int __init arch_probe_nr_irqs(void)
 	int nr;
diff --git a/include/linux/irq.h b/include/linux/irq.h
index d591bfe..3fb6a09 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -580,6 +580,8 @@ static inline struct msi_desc *irq_data_get_msi(struct irq_data *d)
 	return d->msi_desc;
+unsigned int arch_dynirq_lower_bound(unsigned int from);
 int __irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node,
 		struct module *owner);
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 8ab8e93..b88dba1 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -363,6 +363,13 @@ __irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node,
 		if (from > irq)
 			return -EINVAL;
 		from = irq;
+	} else {
+		/*
+		 * For interrupts which are freely allocated the
+		 * architecture can force a lower bound to the @from
+		 * argument. x86 uses this to exclude the GSI space.
+		 */
+		from = arch_dynirq_lower_bound(from);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 787b3a0..fb54ede 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -898,3 +898,8 @@ int __init __weak arch_early_irq_init(void)
 	return 0;
+unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
+	return from;

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