[vfio-users] Z170X IOMMU Groups

[Wei Xu]

On 2016年09月23日 02:47, Nick Sarnie wrote:
> Hi again,
>
> Very much to my surprise, Gigabyte replied and sent me a fixed BIOS. The
> new IOMMU groups (with ACS override patch kernel commandline removed for
> this boot), as well as my lspci information are below. I see four
> messages the following messages in dmesg now:
>
> [    0.523892] pci 0000:00:1c.0: Intel SPT PCH root port ACS workaround
> enabled
> [    0.524031] pci 0000:00:1c.4: Intel SPT PCH root port ACS workaround
> enabled
> [    0.524159] pci 0000:00:1c.5: Intel SPT PCH root port ACS workaround
> enabled
> [    0.524292] pci 0000:00:1d.0: Intel SPT PCH root port ACS workaround
> enabled
>
>
> IOMMU Groups: http://pastebin.com/raw/0dcHk8Xk
> lspci: http://pastebin.com/raw/1zAZuPBM

That's cool, how did you report your issue to Gigabyte? I'd like to have 
a try as well.

Wei

>
> Alex, please let me know if they missed anything else, so I can report
> it to them.
>
> Thanks,
> Nick
>
> On Sun, Sep 18, 2016 at 4:03 PM, Nick Sarnie <commendsarnex at gmail.com
> <mailto:commendsarnex at gmail.com>> wrote:
>
>     Hi again,
>
>     Thanks a lot for investigating. I've reported the issue to the
>     manufacturer.
>
>
>     Thanks,
>     sarnex
>
>     On Sat, Sep 17, 2016 at 5:35 PM, Alex Williamson
>     <alex.l.williamson at gmail.com <mailto:alex.l.williamson at gmail.com>>
>     wrote:
>
>         On Sat, Sep 17, 2016 at 12:29 PM, Nick Sarnie
>         <commendsarnex at gmail.com <mailto:commendsarnex at gmail.com>> wrote:
>
>             Hi Alex,
>
>             The output is here: http://pastebin.com/raw/qjnpuaVr
>             <http://pastebin.com/raw/qjnpuaVr>
>
>
>         Ok, you need to go complain to your motherboard manufacturer,
>         they're the ones hiding the ACS capability.  PCIe capabilities
>         always start at 0x100, the dword there is:
>
>         100: 01 00 01 22 = 0x22010001
>
>         Breaking that down, the capability at 0x100 is ID 0x0001 (AER),
>         version 0x1, and the next capability is at 0x220.  So we do the
>         same there:
>
>         220: 19 00 01 00 = 0x00010019
>
>         Capability ID 0x0019 (Secondary PCIe), version 0x1, next
>         capability 0x0, terminating the capability list.
>
>         Per Intel documentation for the chipset
>         (http://www.intel.com/content/www/us/en/chipsets/100-series-chipset-datasheet-vol-2.html
>         <http://www.intel.com/content/www/us/en/chipsets/100-series-chipset-datasheet-vol-2.html>),
>         the ACS capability and control registers live at 0x144 and 0x148
>         respectively and we can see that you do have data here matching
>         the default value of the capability register:
>
>         140: 00 00 00 00 0f 00 00 00 00 00 00 00 00 00 00 00
>
>         ie. default value of 0x144 is 0xf.  It appears that this BIOS
>         vendor didn't connect the capability into the chain or fill in
>         the capability header.  The registers to do this are RW/O, ie.
>         Read-Write-Once.  IOW, the registers can only be written once,
>         which is intended to be used by the BIOS.  The capability bits
>         themselves are RW/O, allowing vendors to expose different sets
>         of ACS capabilities.  Given that this vendor has not exposed the
>         capability, we have no basis to believe that the default value
>         of the register represents the real capabilities of the system
>         and therefore we cannot assume we're able to control ACS.  File
>         a bug with the vendor or look for a BIOS update where they may
>         have already fixed this.
>
>             Also, is there any way we could move the USB controller into
>             its own group, or remove the Ethernet and SATA controller
>             into a seperate group? Ideally, I could pass the USB
>             Controller in group 7 without the ACS patch.
>
>
>         That's not how IOMMU groups works.  See
>         http://vfio.blogspot.com/2014/08/iommu-groups-inside-and-out.html <http://vfio.blogspot.com/2014/08/iommu-groups-inside-and-out.html>
>           We aren't creating these groups arbitrarily, we base them on
>         the information provided to use by the IOMMU driver and PCI
>         topology features, including ACS.  If we cannot determine that
>         there is isolation between components, we must assume that they
>         are not isolated.  Your choices are to run an unsupported (and
>         unsupportable) configuration using the ACS override patch, get
>         your hardware vendor to fix their platform, or upgrade to better
>         hardware with better isolation characteristics.
>
>
>
>
>
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