linux-kernel - Re: [Bugfix] x86/apic: Fix xen IRQ allocation failure caused by commit b81975eade8c

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Date:	Wed, 07 Jan 2015 23:37:52 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Sander Eikelenboom <linux@...elenboom.it>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Jan Beulich <JBeulich@...e.com>,
	David Rientjes <rientjes@...gle.com>,
	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
	Richard Weinberger <richard@....at>,
	Oren Twaig <oren@...lemp.com>,
	Grant Likely <grant.likely@...aro.org>,
	Prarit Bhargava <prarit@...hat.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Ingo Molnar <mingo@...nel.org>, xen-devel@...ts.xenproject.org
Subject: Re: [Bugfix] x86/apic: Fix xen IRQ allocation failure caused by commit
 b81975eade8c

On 2015/1/7 22:50, Konrad Rzeszutek Wilk wrote:
> On Wed, Jan 07, 2015 at 02:13:49PM +0800, Jiang Liu wrote:
>> Commit b81975eade8c ("x86, irq: Clean up irqdomain transition code")
>> breaks xen IRQ allocation because xen_smp_prepare_cpus() doesn't invoke
>> setup_IO_APIC(), so no irqdomains created for IOAPICs and
>> mp_map_pin_to_irq() fails at the very beginning.
>> --- a/arch/x86/kernel/apic/io_apic.c
>> +++ b/arch/x86/kernel/apic/io_apic.c
>> @@ -2369,31 +2369,29 @@ static void ioapic_destroy_irqdomain(int idx)
>>  	ioapics[idx].pin_info = NULL;
>>  }
>>  
>> -void __init setup_IO_APIC(void)
>> +void __init setup_IO_APIC(bool xen_smp)
>>  {
>>  	int ioapic;
>>  
>> -	/*
>> -	 * calling enable_IO_APIC() is moved to setup_local_APIC for BP
>> -	 */
>> -	io_apic_irqs = nr_legacy_irqs() ? ~PIC_IRQS : ~0UL;
>> +	if (!xen_smp) {
>> +		apic_printk(APIC_VERBOSE, "ENABLING IO-APIC IRQs\n");
>> +		io_apic_irqs = nr_legacy_irqs() ? ~PIC_IRQS : ~0UL;
>> +
>> +		/* Set up IO-APIC IRQ routing. */
>> +		x86_init.mpparse.setup_ioapic_ids();
>> +		sync_Arb_IDs();
>> +	}
> 
> 
> Is there a specific reason that this cannot run in all cases?
> 
> What I am asking is why are we doing a special case here? The description
> at the top implied that we were just missing an call to
> setup_IO_APIC.. 
Hi Konrad,
	I'm not very familiar with Xen IRQ yet, so I just enabled the
code to create irqdomains for IOAPICs and keep other part as is. I will
try to check whether we could enable other part all together:)
Regards!
Gerry

> 
>>  
>> -	apic_printk(APIC_VERBOSE, "ENABLING IO-APIC IRQs\n");
>>  	for_each_ioapic(ioapic)
>>  		BUG_ON(mp_irqdomain_create(ioapic));
>> -
>> -	/*
>> -         * Set up IO-APIC IRQ routing.
>> -         */
>> -	x86_init.mpparse.setup_ioapic_ids();
>> -
>> -	sync_Arb_IDs();
>>  	setup_IO_APIC_irqs();
>> -	init_IO_APIC_traps();
>> -	if (nr_legacy_irqs())
>> -		check_timer();
>> -
>>  	ioapic_initialized = 1;
>> +
>> +	if (!xen_smp) {
>> +		init_IO_APIC_traps();
>> +		if (nr_legacy_irqs())
>> +			check_timer();
>> +	}
>>  }
>>  
>>  /*
>> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
>> index 4c071aeb8417..7eb0283901fa 100644
>> --- a/arch/x86/xen/smp.c
>> +++ b/arch/x86/xen/smp.c
>> @@ -326,7 +326,10 @@ static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
>>  
>>  		xen_raw_printk(m);
>>  		panic(m);
>> +	} else {
>> +		setup_IO_APIC(true);
>>  	}
>> +
>>  	xen_init_lock_cpu(0);
>>  
>>  	smp_store_boot_cpu_info();
>> -- 
>> 1.7.10.4
>>
> --
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