linux-kernel - [PATCH v2] xen/events: Always allocate legacy interrupts on PV guests

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Date:	Wed, 18 Nov 2015 13:14:05 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	konrad.wilk@...cle.com, david.vrabel@...rix.com,
	linux@....linux.org.uk
Cc:	stefano.stabellini@...rix.com, jgross@...e.com, tglx@...utronix.de,
	vkuznets@...hat.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, xen-devel@...ts.xen.org,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH v2] xen/events: Always allocate legacy interrupts on PV guests

After commit 8c058b0b9c34 ("x86/irq: Probe for PIC presence before
allocating descs for legacy IRQs") early_irq_init() will no longer
preallocate descriptors for legacy interrupts if PIC does not
exist, which is the case for Xen PV guests.

Therefore we may need to allocate those descriptors ourselves.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Suggested-by: Thomas Gleixner <tglx@...utronix.de>
---

v2: Use nr_legacy_irqs() instead of NR_IRQS_LEGACY (needs definition for ARM)

 arch/arm/include/asm/irq.h       | 4 ++++
 drivers/xen/events/events_base.c | 5 +++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h
index be1d07d..b864f60 100644
--- a/arch/arm/include/asm/irq.h
+++ b/arch/arm/include/asm/irq.h
@@ -2,6 +2,10 @@
 #define __ASM_ARM_IRQ_H
 
 #define NR_IRQS_LEGACY	16
+static inline int nr_legacy_irqs(void)
+{
+	return NR_IRQS_LEGACY;
+}
 
 #ifndef CONFIG_SPARSE_IRQ
 #include <mach/irqs.h>
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 849500e..524c221 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -39,6 +39,7 @@
 #include <asm/irq.h>
 #include <asm/idle.h>
 #include <asm/io_apic.h>
+#include <asm/i8259.h>
 #include <asm/xen/pci.h>
 #endif
 #include <asm/sync_bitops.h>
@@ -420,7 +421,7 @@ static int __must_check xen_allocate_irq_gsi(unsigned gsi)
 		return xen_allocate_irq_dynamic();
 
 	/* Legacy IRQ descriptors are already allocated by the arch. */
-	if (gsi < NR_IRQS_LEGACY)
+	if (gsi < nr_legacy_irqs())
 		irq = gsi;
 	else
 		irq = irq_alloc_desc_at(gsi, -1);
@@ -446,7 +447,7 @@ static void xen_free_irq(unsigned irq)
 	kfree(info);
 
 	/* Legacy IRQ descriptors are managed by the arch. */
-	if (irq < NR_IRQS_LEGACY)
+	if (irq < nr_legacy_irqs())
 		return;
 
 	irq_free_desc(irq);
-- 
2.1.0

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