linux-kernel - Re: [PATCH v9] irq: add quirk for broken interrupt remapping on 55XX chipsets

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Message-ID: <20130416133555.GB9241@hmsreliant.think-freely.org>
Date:	Tue, 16 Apr 2013 09:35:56 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	linux-kernel@...r.kernel.org, Prarit Bhargava <prarit@...hat.com>,
	Don Zickus <dzickus@...hat.com>,
	Don Dutile <ddutile@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Asit Mallick <asit.k.mallick@...el.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-pci@...r.kernel.org,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Arkadiusz Miśkiewicz <arekm@...en.pl>
Subject: Re: [PATCH v9] irq: add quirk for broken interrupt remapping on 55XX
 chipsets

On Tue, Apr 16, 2013 at 12:24:54PM +0200, Joerg Roedel wrote:
> On Mon, Apr 15, 2013 at 06:41:17PM -0400, Neil Horman wrote:
> > +#ifdef CONFIG_IRQ_REMAP
> > +static void __init intel_remapping_check(int num, int slot, int func)
> > +{
> > +	u8 revision;
> > +
> > +	revision = read_pci_config_byte(num, slot, func, PCI_REVISION_ID);
> > +
> > +	/*
> > +	 * Revision 0x13 of this chipset supports irq remapping
> > +	 * but has an erratum that breaks its behavior, flag it as such
> > +	 */
> > +	if (revision == 0x13)
> > +		irq_remap_broken = 1;
> > +
> > +}
> > +#else
> 
> Any reason why you don't check this in the Intel IOMMU init code? You
> would safe the ifdefs and you don't have to include
> irq-remapping-internal header files somewhere else in the tree.
> 
> 
> 	Joerg
> 
> 
> 
Actually, hold on that last note, the intel iommu init code doesn't seem to
create any direct relationship between the set of iommu's and the pci_dev's that
implement them.  In the intel_irq_remapping_supported path I can loop over each
dmar_dhrd_unit, and interrogate each of the devices on its **devices list to see
if the device/vendor and revision ids match, but looking at the dhrd parsing
code, I'm not sure the iommu pci_dev is always going to be on that list.  That
seems like its going to be pretty ugly in and of itself.  Do you have a
suggested way to identify the pci_dev of the device we need in that path without
having to simply iterate over every device in that scope?

Neil

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