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

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Message-ID: <alpine.DEB.2.02.1511201634500.1107@kaball.uk.xensource.com>
Date:	Fri, 20 Nov 2015 16:35:01 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:	<konrad.wilk@...cle.com>, <david.vrabel@...rix.com>,
	<linux@....linux.org.uk>, <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>
Subject: Re: [PATCH] xen/events: Always allocate legacy interrupts on PV
 guests

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@...cle.com>
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>

Acked-by: Stefano Stabellini <stefano.stabellini@...citrix.com>


> 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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