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[Xen-users] Xen domu state in blocking for vt-d hardware access


I am running Xen 4.0.1 with Debian Squeeze dom0. I have VT-D enabled
motherboard, and has confirmed working for vt-d PCI passthrough. When
I am trying to passthrough on-board sound card
"00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio
Controller (rev 02)"
I found both PV-domU and HVM domU does NOT function well with this
sound card at all. There are always huge noise from speaker. So I
tested the sound card and speaker, which both functioning fine under
dom0. I then found the sound card does produce same quality sound as
long as the domU guest running stats is in r (running), if it stay in
b (blocking) then there is either no sound at all or just noise.

I get the domU running stats from
sudo xm list

Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0   508     1     r-----   2011.5
ares                                        15  2048     1     r-----   7778.3
palace                                      14   512     1     -b----   2885.3
palace-test                                 16   512     1     -b----     63.8

Just to be clear the domU guest I have tested with vt-d PCI
passthrough is HVM win7 32 bit, and PV-domU debian Squeeze.

I tried to solve the "issue" by doing following, and none of them worked.

1. pin the dom0 to specific CPU core, e.g. 0, and assign domU to
different core e.g. 1-3.
2. change xm sched-credit -d <domain> -w 65595 or other higher then default 256.

So my question is how to allow domU guest to stay in runing, so it can
have access to the sound card all the time. At the moment, it seems
something keep making it changing to blocking status, which clearly
make impossible to play music. Or this is a bug.


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