linux-kernel - Re: [PATCH] pci: change msi-x vector to 32bit

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Message-ID: <86802c440808161517y1eaa5a4eo817b8a1bf75945be@mail.gmail.com>
Date:	Sat, 16 Aug 2008 15:17:35 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"James Bottomley" <James.Bottomley@...senpartnership.com>
Cc:	"Alan Cox" <alan@...rguk.ukuu.org.uk>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Jesse Barnes" <jbarnes@...tuousgeek.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	"Andrew Vasquez" <andrew.vasquez@...gic.com>
Subject: Re: [PATCH] pci: change msi-x vector to 32bit

On Sat, Aug 16, 2008 at 1:45 PM, James Bottomley
<James.Bottomley@...senpartnership.com> wrote:
>> > What I still don't quite get is the benefit of large IRQ spaces ...
>> > particularly if you encode things the system doesn't really need to know
>> > in them.
>>
>> then set nr_irqs = nr_cpu_ids * NR_VECTORS))
>> and count down for msi/msi-x?
>
> No, what I mean is that msis can trip directly to CPUs, so this is an
> affinity thing (that MSI is directly bound to that CPU now), so in the
> matrixed way we display this in show_interrupts() with the CPU along the
> top and the IRQ down the side, it doesn't make sense to me to encode IRQ
> affinity in the irq number again.   So it makes more sense to assign the
> vectors based on both the irq number and the CPU affinity so that if the
> PCI MSI for qla is assigned to CPU4 you can reassign it to CPU5 and so
> on.

msi-x entry index, cpu_vector, irq number...

you want to different cpus have same vector?

YH
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