Re: VT-d interrup remapping errata workaround

[Malcolm Crossley <malcolm.crossley@citrix.com>]

On 08/07/13 13:29, Jan Beulich wrote:
> All,
>
> just having spotted the backport of Linux commit 03bbcb2e I notice
> a certain discrepancy with the Xen commit having the same purpose
> as well as with the actual specification updates:
>
> The Linux solution keys off of device IDs 3403 and 3406, as listed in
> the specification update, but this way fails to cover the X58 chipset,
> which has - under different numbers (62 and 69) - the same errata
> (the Linux commit message also only mentions erratum 53 for the
> 55x0 chipsets, albeit I believe 47 is as much of an issue there as it is
> for Xen).
>
> The Xen solution keys off of ID 342e, with no explanation in the
> commit description on where this association comes from.
>
> I therefore wonder whether
> - the Xen solution may have false positives
> - the Linux solution would still have false negatives even after
>    adding ID 3405
>
> Jan
>
Hi Jan,

I have used the VT-d control PCI device which is common across X58/5520/5500

See page 233 
http://www.intel.co.uk/content/dam/doc/datasheet/x58-express-chipset-datasheet.pdf

and

page 255 
http://www.intel.co.uk/content/dam/doc/datasheet/5520-5500-chipset-ioh-datasheet.pdf

It seems the Linux workaround only applies to the 5520 and 5500 chipsets.

The pci ID database suggests 0x342e will detect 7500 chipset (which does 
not have the interrupt remapping errata) but that chipset never reports 
revision 0x13 so the errata workaround will never be applied.

Malcolm