linux-kernel - Re: [PATCH 2/5] irqchip: gicv3-its: zero itt before handling to hardware

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Date:	Fri, 30 Jan 2015 19:24:53 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Yun Wu <wuyun.wu@...wei.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"jason@...edaemon.net" <jason@...edaemon.net>
CC:	"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 2/5] irqchip: gicv3-its: zero itt before handling to hardware

On 30/01/15 07:46, Yun Wu wrote:
> Some kind of brain-dead implementations chooses to insert ITEes in
> rapid sequence of disabled ITEes, and an un-zeroed ITT will confuse
> ITS on judging whether an ITE is really enabled or not. Considering
> the implementations are still supported by the GICv3 architecture,
> in which ITT is not required to be zeroed before being handled to
> hardware, we do the favor in ITS driver.
> 
> Signed-off-by: Yun Wu <wuyun.wu@...wei.com>
> ---
>  drivers/irqchip/irq-gic-v3-its.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index a391417..2a08d85 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -1063,7 +1063,7 @@ static struct its_device *its_create_device(struct its_node *its, u32 dev_id,
>  	nr_ites = max(2UL, roundup_pow_of_two(nvecs));
>  	sz = nr_ites * its->ite_size;
>  	sz = max(sz, ITS_ITT_ALIGN) + ITS_ITT_ALIGN - 1;
> -	itt = kmalloc(sz, GFP_KERNEL);
> +	itt = kzalloc(sz, GFP_KERNEL);
>  	lpi_map = its_lpi_alloc_chunks(nvecs, &lpi_base, &nr_lpis);
> 
>  	if (!dev || !itt || !lpi_map) {

Fair enough. I suppose this cannot really hurt if we have stupid HW around.

Acked-by: Marc Zyngier <marc.zyngier@....com>

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