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[Xen-users] RMRR and HDMI sound issues with Xen 4.7.0, vga-passthrough, IGD

  • To: xen-users@xxxxxxxxxxxxx
  • From: Cloudee Huang <cloudeecn@xxxxxxxxx>
  • Date: Thu, 11 Aug 2016 11:44:33 -0400
  • Delivery-date: Thu, 11 Aug 2016 15:45:42 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>

Hi All,

I just upgraded Xen from 4.5.3 to 4.7.0, everything works fine except
following 2 issues, both related to vga-passthrough:

1. Lots of messages like following floods 'xl dmesg'

[VT-D]DMAR:[DMA Write] Request device [0000:00:02.0] fault addr
dbxxxxxx, iommu reg = ……

while using vga-passthrough (both traditional mode and new IGD mode).
The related address falls well in the address range by RMRR. It’s OK
to start Linux and X, but will crash Windows.

I have dug into the xen-devel mail list and found a patch in following thread:


Though the follow-ups of this thread indicates the fix should be on
p2m.c, I patched the xen/drivers/passthrough/vtd/iommu.c and the issue
is fixed.

By the way, I found some intel_iommu_(un)map_page calling were added
into (set/clear)_identity_p2m_entry() function in p2m.c after that
thread in 4.7.0 code but the issue still exists. Maybe there are still
some un-handled corner cases?

2. Can’t play any sound through HDMI port of IGD with sample-rate more
than 32000Hz, either in fresh booted Dom0 or vga-passthroughed DomU.

I tried kernel 4.1/4.4/4.6 under Xen 4.5/4.6/4.7, all without luck.
Booting the same OS without Xen works fine in all supported
sample-rate (32000/44100/48000Hz in my case). That’s really weird for
being no good even in Dom0 and being good for a lower sample-rate. I
dug through google as much as I can and found no clues. There is no
error message while playing/initializing hda too.

Dom0, ALSA only, all default config:
# speaker-test -r 32000 -D hw:0,3 -c 2
>>> Sounds OK

# speaker-test -r 44100 -D hw:0,3 -c 2
>>> No sound or a short click sound

# speaker-test -r 48000 -D hw:0,3 -c 2
>>> No sound or a short click sound

Direct boot into the same system with Xen:
>>> Sound works well in any sample-rate

Software I’m using:
Alpine linux 3.4.2 / Archlinux
Kernel: 4.4.15 x86_64 /
Xen: 4.7.0

NUC 54250WYK (CPU: i5-4250U) , connected to a TV via HDMI port.

#aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: HDMI [HDA Intel HDMI], device 3: HDMI 0 [HDMI 0] <==== I’m
using this port.
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA Intel HDMI], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA Intel HDMI], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 0: ALC283 Analog [ALC283 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

# lspci
00:00.0 Host bridge: Intel Corporation Haswell-ULT DRAM Controller (rev 09)
00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT
Integrated Graphics Controller (rev 09)
00:03.0 Audio device: Intel Corporation Haswell-ULT HD Audio Controller (rev 09)
00:14.0 USB controller: Intel Corporation 8 Series USB xHCI HC (rev 04)
00:16.0 Communication controller: Intel Corporation 8 Series HECI #0 (rev 04)
00:19.0 Ethernet controller: Intel Corporation Ethernet Connection
I218-V (rev 04)
00:1b.0 Audio device: Intel Corporation 8 Series HD Audio Controller (rev 04)
00:1d.0 USB controller: Intel Corporation 8 Series USB EHCI #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation 8 Series LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 8 Series SATA Controller 1
[AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 8 Series SMBus Controller (rev 04)

Thanks for your attention.

Cloudee Huang
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