linux-kernel - Re: [PATCH 1/5] gic: prevent gic from crossing NR

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Message-ID: <20100127224309.GD29665@n2100.arm.linux.org.uk>
Date:	Wed, 27 Jan 2010 22:43:09 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	adharmap@...eaurora.org
Cc:	linux-arm-kernel@...ts.infradead.org, Ingo Molnar <mingo@...e.hu>,
	Catalin Marinas <catalin.marinas@....com>,
	Yinghai Lu <yinghai@...nel.org>,
	Tony Lindgren <tony@...mide.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Kalle Valo <kalle.valo@....fi>, Jean Pihet <jpihet@...sta.com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Colin Tuckley <colin.tuckley@....com>,
	Philby John <pjohn@...mvista.com>,
	Srinidhi Kasagar <srinidhi.kasagar@...ricsson.com>,
	Alessandro Rubini <rubini@...pv.it>,
	Andrea Gallo <andrea.gallo@...ricsson.com>,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	Abhijeet Dharmapurikar <adharmap@...cinc.com>
Subject: Re: [PATCH 1/5] gic: prevent gic from crossing NR_IRQ

On Wed, Jan 27, 2010 at 11:32:25AM -0800, adharmap@...eaurora.org wrote:
> From: Abhijeet Dharmapurikar <adharmap@...cinc.com>
> 
> The gic code tries to initialize interrupts beyond NR_IRQ. Prevent
> code from doing that.

NAK.  This is completely the wrong approach.

        /*
         * Find out how many interrupts are supported.
         */
        max_irq = readl(base + GIC_DIST_CTR) & 0x1f;
        max_irq = (max_irq + 1) * 32;

        /*
         * The GIC only supports up to 1020 interrupt sources.
         * Limit this to either the architected maximum, or the
         * platform maximum.
         */
        if (max_irq > max(1020, NR_IRQS))
                max_irq = max(1020, NR_IRQS);
...
        for (i = irq_start; i < gic_data[gic_nr].irq_offset + max_irq; i++) {

This function is broken if irq_start != 0, and needs fixing - max_irq
needs to be limited to the _minimum_ of 1020 or NR_IRQS - irq_start.
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