Re: Regression in kernel 4.2.3+ (relative to 4.1.10) on AMD 990FX system with IOMMU enabled

[Mark Hounschell <markh-n2QNKt385d+sTnJN9+BGXg@public.gmane.org>]

On 11/04/2015 04:08 PM, Alex Williamson wrote:
> On Wed, 2015-11-04 at 12:24 -0500, Laine Stump wrote:
>> Last week I upgraded my Fedora 22 AMD 990FX system from kernel 4.1.10 to
>> 4.2.3 (standard Fedora builds) and multiple devices stopped working:
>>
>> * 00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] SBx00
>> Azalia (Intel HDA) (rev 40)
>>
>> * 02:00.[01] Ethernet controller: Intel Corporation 82576 Gigabit
>> Network Connection
>>
>> * 01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Cedar
>> HDMI Audio [Radeon HD 5400/6300 Series]
>>
>> (The 1st is integrated on the motherboard, the 2nd & 3rd are behind an
>> AMD RD890 pci-pci bridge. There may be other devices failing, but these
>> are the ones immediately obvious.)
>>
>> Whatever is the source of the failure, it ends up that the drivers for
>> these devices aren't loaded.
>>
>> At Alex Williamson's suggestion, I tried disabling IOMMU in the BIOS,
>> and magically all the devices resumed normal operation (except that I
>> can't do vfio device assignment because the IOMMU is disabled).
>>
>> Reverting to kernel 4.1.10 very definitely eliminates the problem. I've
>> also tried kernel 4.2.5 and it has the same problem as 4.2.3 (these
>> three are the only pre-built kernels for F22). I can provide dmesg /
>> lspci output from each of these, or any other debug info anyone might
>> like me to gather.
>
> I built a 4.2.3 kernel for my 990fx system and can't seem to reproduce
> it.  Does 'lspci -k' for those devices show any driver?  Does 'lsmod'
> show the drivers loaded, igb and snd_hda_intel?  If not, does manually
> modprobe'ing either of those drivers change anything?  You haven't
> installed a script that writes to driver_override or setup a
> configuration where those devices are claimed by pci-stub and forgotten
> about it, have you? (it's happened to me)  Otherwise, dmesg is probably
> a good place to start.  Thanks,
>
> Alex

I'm also running one of these with a 4.2.5 kernel with no IOMMU issues.

mark