Re: [PATCH] xen/events: Always allocate legacy interrupts on PV guests

[Boris Ostrovsky]

On 11/20/2015 11:35 AM, Stefano Stabellini wrote:
> On Fri, 20 Nov 2015, Boris Ostrovsky wrote:
> > 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@xxxxxxxxxx>
> > Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

I realized that I neglected to add ARM64 maintainers here. Adding them now.

(And this also need an ACK/NACK from Russell)

-boris

> > v3: Add arm64 definition of nr_legacy_irqs()
> >
> >   arch/arm/include/asm/irq.h       | 4 ++++
> >   arch/arm64/include/asm/irq.h     | 6 ++++++
> >   drivers/xen/events/events_base.c | 5 +++--
> >   3 files changed, 13 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/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
> > index 23eb450..24ba8d8 100644
> > --- a/arch/arm64/include/asm/irq.h
> > +++ b/arch/arm64/include/asm/irq.h
> > @@ -7,4 +7,10 @@ struct pt_regs;
> >   
> >   extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
> >   
> > +#define NR_IRQS_LEGACY  0
> > +static inline int nr_legacy_irqs(void)
> > +{
> > +	return NR_IRQS_LEGACY;
> > +}
> > +
> >   #endif
> > 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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