Buss Reset Problem

Michal Kazior michal.kazior at tieto.com
Thu Jul 9 06:46:55 PDT 2015

On 9 July 2015 at 15:33,  <CACook at quantum-sci.com> wrote:
> On Monday 06 July 2015 8:04:39 CACook at quantum-sci.com wrote:
>> CPU: Intel(R) Xeon(R) CPU E3-1265L v3 @ 2.50GHz
>> KVM: qemu-kvm-1.5.3-86.el7_1.2.x86_64
>> Kernel: 4.1.1-1.el7.elrepo.x86_64, and kernel-3.10.0-229.7.2.el7.x86_64
>> Host & Guest: CentOS 7.1
>> Using virt-manager-1.1.0-12.el7.noarch to create, configure, and start guest
>> I am trying to do a PCI passthrough of a QCA988X wifi card. It's a Doodle Labs military-grade 802.11ac miniPCI card. This card configures nicely on the host, and seems to pass through to the KVM guest, but early in the boot of the guest it says "Unknown header type" at the wifi's bus address. And sure enough, lspci -vv on the host then shows:
>>         !!! Unknown header type 7f
>>         Kernel driver in use: vfio-pci
>> It seems to be the buss reset problem, as outlined here:
>> http://www.gossamer-threads.com/lists/linux/kernel/2054846
>> ... Except my card locks up on boot of the KVM guest.
>> When I logged a bug at QEMU (https://bugs.launchpad.net/qemu/+bug/1471583), Alex suggested I add to the patch:
>> DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x003c, quirk_no_bus_reset);
>> ... So I am in the process of trying that now.
> So that's it for the Doodle Labs ACE-DB-3.  It went back yesterday -- doesn't work with Linux.

I think someone complained they couldn't get an XB design to work on
some of their PCI-E hosts (some Atom laptop even refused to POST with
the card if I recall correctly). Apparently there's an electrical
quirk - or at least that was to conclusion back then.

> It's not the buss reset problem as I patched quirks.c.

I wonder how much related this could be to Data Bus Error ath10k sees
when doing cold resets sometimes. Maybe it's good to have the quirk
fixup nonetheless? But I'm no PCI expert so what do I know.


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