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

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Message-ID: <alpine.DEB.2.02.1511201535550.1107@kaball.uk.xensource.com>
Date:	Fri, 20 Nov 2015 15:36:39 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	<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>,
	Catalin Marinas <catalin.marinas@....com>,
	"Will Deacon" <will.deacon@....com>
Subject: Re: [PATCH v2] xen/events: Always allocate legacy interrupts on PV
 guests

On Fri, 20 Nov 2015, Boris Ostrovsky wrote:
> On 11/20/2015 06:24 AM, Stefano Stabellini wrote:
> > On Wed, 18 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>
> > You need to do this for arm64 too.
> > 
> > FYI you can download arm64 cross-compilers from
> > https://releases.linaro.org/14.04/components/toolchain/binaries/
> > then you can use them by exporting ARCH=arm64 and
> > CROSS_COMPILE=/path/to/gcc-linaro-aarch64-linux-gnu-version/bin/aarch64-linux-gnu-
> 
> I did test on arm but didn't realize that arm64 uses different include files.
> 
> Does arm64 not have any legacy interrupts?
> 
> BTW, I got this build error:
> 
>   STUBCPY drivers/firmware/efi/libstub/lib-sort.stub.o
> 0000000000000000 R_AARCH64_ABS64   __efistub_sort
> 0000000000000008 R_AARCH64_ABS64   .init__ksymtab_strings
> drivers/firmware/efi/libstub/lib-sort.stub.o: absolute symbol references not
> allowed in the EFI stub
> drivers/firmware/efi/libstub/Makefile:63: recipe for target
> 'drivers/firmware/efi/libstub/lib-sort.stub.o' failed
> make[4]: *** [drivers/firmware/efi/libstub/lib-sort.stub.o] Error 1
> scripts/Makefile.build:403: recipe for target 'drivers/firmware/efi/libstub'
> failed
> make[3]: *** [drivers/firmware/efi/libstub] Error 2
> scripts/Makefile.build:403: recipe for target 'drivers/firmware/efi' failed
> make[2]: *** [drivers/firmware/efi] Error 2
> scripts/Makefile.build:403: recipe for target 'drivers/firmware' failed
> make[1]: *** [drivers/firmware] Error 2
> Makefile:943: recipe for target 'drivers' failed
> make: *** [drivers] Error 2
> 
> I worked around this by removing some of EFI config options but presumably
> this needs to be properly fixed.

Interesting. This build error could be something new. Could you please
post your kernel config?


> > > 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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