[vfio-users] Intel LGA 1151 Kaby Lake Chipsets and PCIe ACS

[Alex Williamson]

On Fri, 6 Jan 2017 11:22:33 +0000
Zir Blazer <zir_blazer at hotmail.com> wrote:

> As everyone knows by now, the Skylake refresh, Kaby Lake, was released a few days ago as the new 7th gen Core Processors. This includes the Union Point Chipsets (200 Series) for LGA 1151, which are the B250, Q250, Q270, H270, Z270, and possibily at least one more Chipset for Xeons E3 1200v6, which is rumored to be the C422 according to available info (It was not officially released as far that I know, nor the Xeons E3 1200v6).
> 
> 
> If I recall correctly, when the Skylake platform was first released, there was something broken in the Sunrise Point Chipsets related to PCIe ACS support, thus the IOMMU Grouping of the Chipset integrated Devices and its PCIe Slots was extremely ugly. A quirk for that was included in the Linux Kernel, and everyone was happy. But with the new Chipsets, it seems that we will need new quirks...
> 
> 
> According to the 200 Series Chipset Family PCH Spec Update, here:
> 
> <http://www.intel.com/content/www/us/en/chipsets/200-series-chipset-pch-datasheet-vol-1.html>http://www.intel.com/content/www/us/en/chipsets/200-series-chipset-pch-spec-update.html
> 
> 
> They have the Errata 22, which is that PCIe ACS is at a different offset than expected. This looks to be the very same Errata 23 than the previous Skylake Sunrise Point Chipsets had, which I suppose that is what got fixed last time:
> 
> http://www.intel.la/content/www/xl/es/chipsets/100-series-chipset-spec-update.html
> 
> 
> Basically, the new Motherboards with Union Point Chipsets should have broken IOMMU Grouping in the same fashion as Sunrise Point, but should be fixeable.
> 
> 
> So, I'm sending this to be one step ahead of the Kaby Lake early adopters that will for sure eventually report this :D


Thanks for this, and especially for finding the errata that indicates
Union Point has the same bug, that's critical for supporting a patch.
I've just posted this:

https://lkml.org/lkml/2017/1/19/458

Hopefully it'll be fixed starting in the v4.11 kernel.  Thanks,

Alex