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From: Jesse Barnes <jbarnes@virtuousgeek.org>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: [PATCH 5/8] PCI PCIe portdrv: Fix allocation of interrupts
Date: Fri, 9 Jan 2009 15:33:43 -0800
User-Agent: KMail/1.9.10
Cc: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>,
       Linux PCI <linux-pci@vger.kernel.org>,
       LKML <linux-kernel@vger.kernel.org>
References: <200901042346.42723.rjw@sisk.pl> <200901081753.01637.rjw@sisk.pl> <200901082145.39429.rjw@sisk.pl>
In-Reply-To: <200901082145.39429.rjw@sisk.pl>
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On Thursday, January 8, 2009 12:45 pm Rafael J. Wysocki wrote:
> On Thursday 08 January 2009, Rafael J. Wysocki wrote:
> > On Thursday 08 January 2009, Kenji Kaneshige wrote:
> > > Rafael J. Wysocki wrote:
> > > > On Thursday 08 January 2009, Kenji Kaneshige wrote:
> > > >> Rafael J. Wysocki wrote:
> > > >>> From: Rafael J. Wysocki <rjw@sisk.pl>
> > > >>>
> > > >>> If MSI-X interrupt mode is used by the PCI Express port driver, too
> > > >>> many vectors are allocated and it is not ensured that the right
> > > >>> vectors will be used for various services.  Namely, the PCI Express
> > > >>> specification states that both PCI Express native PME and PCI
> > > >>> Express hotplug will always use the same MSI or MSI-X message for
> > > >>> signalling interrupts, which implies that the same vector will be
> > > >>> used by both of them.  Also, the VC service does not use interrupts
> > > >>> at all. Moreover, is not clear which of the vectors allocated by
> > > >>> pci_enable_msix() will be used for PME and hotplug and which of
> > > >>> them will be used for AER if all of these services are configured.
> > > >>>
> > > >>> For these reasons, rework the allocation of interrupts for PCI
> > > >>> Express ports so that at most two vectors are allocated and ensure
> > > >>> that the right vector will be used for the right purpose.
>
> Appended is a cleaned-up version of the patch that also contains comments
> with references to the appropriate sections of the PCI Express spec.

We'll need testing here in any case; I'll have to re-read the specs carefully 
to see if we can really rely on the vector numbers you have here (at first 
glance Kenji-san's approach seems more robust).

-- 
Jesse Barnes, Intel Open Source Technology Center
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