linux-kernel - Re: [PATCH 07/14] genirq: Add a new generic IPI reservation code to irq core

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Message-ID: <56407055.6080602@imgtec.com>
Date:	Mon, 9 Nov 2015 10:07:17 +0000
From:	Qais Yousef <qais.yousef@...tec.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	<linux-kernel@...r.kernel.org>, <jason@...edaemon.net>,
	<marc.zyngier@....com>, <jiang.liu@...ux.intel.com>,
	<ralf@...ux-mips.org>, <linux-mips@...ux-mips.org>
Subject: Re: [PATCH 07/14] genirq: Add a new generic IPI reservation code to
 irq core

On 11/07/2015 01:31 PM, Thomas Gleixner wrote:
> On Tue, 3 Nov 2015, Qais Yousef wrote:
>> +
>> +	/* always allocate a virq per cpu */
>> +	nr_irqs = ipi_mask_weight(dest);
> That's not really a good assumption. Not all architectures need
> seperate interrupt numbers / descriptors because they can allocate
> from a per cpu interrupt space. We really want to handle that here as
> well. So we need a flag in the IPI domain which tells us whether that
> allocation needs to be weight(desc) or 1.

OK. But is it bad to always allocate the weight? I thought allocating 
virqs is cheap, or maybe not?

Thanks,
Qais
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