linux-kernel - RE: [PATCH] x86/ioapic: Fix the vector

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Date:	Tue, 30 Oct 2012 01:11:53 +0000
From:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
To:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
CC:	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] x86/ioapic: Fix the vector_irq[] is corrupted randomly



> -----Original Message-----
> From: Siddha, Suresh B
> Sent: Tuesday, October 30, 2012 4:24 AM
> To: Liu, Chuansheng
> Cc: mingo@...hat.com; hpa@...or.com; tglx@...utronix.de;
> yinghai@...nel.org; x86@...nel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] x86/ioapic: Fix the vector_irq[] is corrupted randomly
> 
> On Tue, 2012-10-30 at 00:15 +0800, Chuansheng Liu wrote:
> > Not all irq chips are IO-APIC chip.
> >
> > In our system, there are many demux GPIO interrupts except for the
> > io-apic chip interrupts, and these GPIO interrupts are belonged
> > to other irq chips, the chip data is not type of struct irq_cfg
> > either.
> >
> > But in function __setup_vector_irq(), it listed all allocated irqs,
> > and presume all irq chip is ioapic_chip and the chip data is type
> > of struct irq_cfg, it possibly causes the vector_irq is corrupted
> > randomly.
> >
> > For example, one irq 258 is not io-apic chip irq, in __setup_vector_irq(),
> > the chip data is forced to be used as struct irq_cfg, then the value
> > cfg->domain and cfg->vector are wrong to be used to write vector_irq:
> > 		vector = cfg->vector;
> > 		per_cpu(vector_irq, cpu)[vector] = irq;
> >
> > This patch use the .flags to identify if the irq chip is io-apic.
> 
> I have a feeling that your gpio driver is abusing the 'chip_data' in the
> struct irq_data. Shouldn't the driver be using 'handler_data' instead?
Not abusing.

There are many driver codes which has their own chip and chip_data.
For example,
langwell_gpio.c, the chip_data type is struct lnw_gpio;
gpio_omap.c, the chip_data type is struct gpio_bank;

In these cases, if we abused the gpio chip_data type with struct irq_cfg,
we will get very wrong cfg->vector, the value maybe 1 or 1000, anyway,
it is a random value.
> 
> From include/linux/irq.h:
>  * @handler_data:       per-IRQ data for the irq_chip methods
>  * @chip_data:          platform-specific per-chip private data for the chip
>  *                      methods, to allow shared chip implementations
> 
> Also, how are these routed to the processors and the mechanism of the
> vector assignment for these irq's? I presume irq_cfg is needed for the
> setup and the interrupt migration from one cpu to another.
Normally gpio chip just has only one base irq is related with io-apic interrupt,
other allocated *VIRTUAL* irqs are based on this base irq, so no vector assign to them.

But in code __setup_vector_irq(), it list all allocated irqs which include the *VIRTUAL* irqs,
It causes this case that chip_data type is abused.

> 
> What am I missing?
> 
> thanks,
> suresh