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

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 10/04/2013 06:29 PM, Bjorn Helgaas wrote:
> [+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).
Just out of interest, have you tried without Xen, with a normal kernel 
with full virtualization support with intel_iommu=1 (or equivalent AMD 
option)? If you still get the same problem it is likely the same issue I 
have with phantom PCI bridges.
Gordan

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