linux-kernel - Re: [PATCH 5/8] PCI PCIe portdrv: Fix allocation of interrupts

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Message-ID: <496ED6BA.6060500@jp.fujitsu.com>
Date:	Thu, 15 Jan 2009 15:24:58 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/8] PCI PCIe portdrv: Fix allocation of interrupts

Rafael J. Wysocki wrote:
> On Wednesday 14 January 2009, Rafael J. Wysocki wrote:
>> On Wednesday 14 January 2009, Kenji Kaneshige wrote:
> [...]
>>> I'm sorry but I don't understand what the problem is.
>>> Do you mean pci_disable_msix() doesn't work on some platforms?
>> No, I don't.  It was just confusion on my side, sorry.
>>
>> Please have a look at the new version of the patch I sent yesterday
>> (http://marc.info/?l=linux-pci&m=123185510828181&w=4).
> 
> BTW, in your patch the first dummy pci_enable_msix() allocates just one
> vector, which means that the contents of both
> msix_entries[idx_hppme].entry and msix_entries[idx_aer].entry will be the same,
> if my reading of the spec (PCI 3.0 in this case) is correct.
> 
> However, if the second pci_enable_msix() allocates two vectors, the contents of the
> message number fields in the PCIE_CAPABILITIES_REG and PCI_ERR_ROOT_STATUS
> registers may change as a result.
> 

For MSI, the interrupt message number field may change if the Multiple
Message Enable Field was changed. On the other hand, for MSI-X, I think
the interrupt message number field is constant. This is what the "[...]
For a given MSI-X implementation, the entry must remain constant. [...]"
explains in PCI Express spec, I think.

Thanks,
Kenji Kaneshige


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