linux-kernel - Re: [PATCH v2 3/6] irqchip: gicv3-its: limit order of DT size to MAX

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Message-ID: <20150217091945.1c47e92f@arm.com>
Date:	Tue, 17 Feb 2015 09:19:45 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Yun Wu <wuyun.wu@...wei.com>
Cc:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"jason@...edaemon.net" <jason@...edaemon.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 3/6] irqchip: gicv3-its: limit order of DT size to
 MAX_ORDER

On Sun, 15 Feb 2015 09:32:00 +0000
Yun Wu <wuyun.wu@...wei.com> wrote:

> When required DT size is out of the kmalloc()'s capability, the whole

Nit: Using the DT acronym is very confusing here, as it means "Device
Tree" to most people, including me. Please use "Device Table" instead.

Also, the reference to kmalloc is wrong, as we're really using the page
allocator.

> ITS will fail in probing. This actually is not the hardware's problem
> and is mainly a limitation of the kernel memory allocator. This patch
> will keep ITS going on to the next initializaion step with an explicit
> warning.
> 
> Signed-off-by: Yun Wu <wuyun.wu@...wei.com>
> ---
>  drivers/irqchip/irq-gic-v3-its.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c
> b/drivers/irqchip/irq-gic-v3-its.c index f5bfa42..de36606 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -828,6 +828,12 @@ static int its_alloc_tables(struct its_node *its)
>  			u32 ids = GITS_TYPER_DEVBITS(typer);
> 
>  			order = get_order((1UL << ids) * entry_size);
> +			if (order >= MAX_ORDER) {
> +				pr_warn("%s: DT size too large,
> reduce to %u pages\n",
> +
> its->msi_chip.of_node->full_name,
> +					1 << order);
> +				order = MAX_ORDER;
> +			}
>  		}

Something is wrong here. Either (order == MAX_ORDER) is acceptable, or
it is not. Also, your warning says that you're reducing the size to a
new value, but you're displaying the size you can't handle. That
message should be fixed.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.
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