Re: [Xen-devel] ASMedia ASM1083/1085 rev3 and Xen DMA Failure

[Bjorn Helgaas <bhelgaas@xxxxxxxxxx>]

[+cc Konrad, xen-devel]

On Wed, Oct 02, 2013 at 04:43:46PM -0400, Aaron Opfer wrote:
> First time submitting the kernel dev list, so if I have demonstrated
> gross incompetence in some way, please cut me some slack. :)
> 
> I discussed with Clemens Ladisch an issue I was having that I thought
> was related to the driver he authored for my soundcard, but on his
> suggestion I experimented with other PCI devices and we have narrowed
> the issue to the PCI Bridge.
> 
> What hints me toward DMA handling being the fault is the following
> message I receive during kernel initialization after rebooting from an
> Xen hypervisor into a baremetal-kernel, without a power-cycle:
> 
> [0.012815] dmar: DRHD: handling fault status reg 3
> [0.012868] dmar: DMAR:[DMA Read] Request device [07:00.0] fault addr 7e00000
> [0.012868] DMAR:[fault reason 02] Present bit in context entry is clear

Presumably 07:00.0 is your soundcard, and apparently it did a DMA
read to 0x7e00000, which wasn't mapped by the IOMMU.

> In addition to other hints, such as simple IO like changing the active
> port on the soundcard worked (I could hear the relays clicking) but
> not the functions that DMA would be used (streaming audio).
> 
> The PCI devices in my system are connected via this device, as listed by 
> lspci:
> 
> 06:00.0 PCI bridge: ASMedia Technology Inc. ASM1083/1085 PCIe to PCI
> Bridge (rev 03)
> 
> This PCI bridge works under bare-metal Linux normally (w/ various
> debian kernels stable/unstable/testing/backports), but under Xen
> Hypervisor the PCI devices connected exhibit bad behavior.

So it fails with Xen but works otherwise?  I assume there are other
PCI devices, too?  Do they work?

If you want to open a report at http://bugzilla.kernel.org, that would
be a handy place to attach a complete dmesg log and "lspci -vv" output
for more details.

> For
> instance, aformentioned sound card outputs no sound and gets no
> microphone input at all, and an ethernet card causes a system lockup
> as soon as gnome's network manager attempts DHCP over it (presumably;
> I did not test this as thoroughly as the sound card).
> 
> I've used Xen Hypervisors 4.1 and 4.2 and had the issues I described
> above with both of them. I was briefly running 4.3 but I did not test
> the device.
> 
> Rev1 of the ASM1083 was apparently buggy to the point of being
> unusable, as Clemens pointed out. I would be disappointed if this
> device is similarly unsalvageable,but would be happier if this buggy
> hardware at the very least outputted warnings to users who attempt to
> use it (in Xen).
> 
> All The Best,
> 
> Aaron Opfer
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