[Xen-users] VT-d "partial" success - passing DVB-S tuner to Windows DomU (based off previous thread of similar name!)

[Daniel Kao <dkao@xxxxxxxxxxxx>]

Hi All,

So I've got a DVB-S PCI Express card ($30 USD Twinhan AD-SE200 off eBay) that's being passed via VT-d/pciback in Xen 3.2.1 under CentOS 5.2 to a Windows XP SP3 which works! ... except for one small issue...

Motherboard is an Intel DQ35JO that much people has had success with and an Intel E8400 CPU.

The issue is that when dealing with FTA MPEG-2 transport streams (DVB-S based @ Galaxy 25 @ 97.0W), all is well until I start putting a slight I/O (whether disk or otherwise) load under dom0.  The issue is very similar and indicative of TV tuner cards and other PCI devices which have poorly matched PCI latency timers.  Basically when dom0 isn't under load, the DVB-S card and Windows XP SP3 works great.  Once there's a slight load (I/O load; not CPU) in dom0, I get continuity errors in the MPEG-2 packet transport stream.  Normally, this is an issue with signal strength of the receiving satellite, but this is not the issue.  These continuity errors are easily reproducible.  All I have to do is log into my CentOS dom0's gnome desktop via vnc (thru vncserver), launch the "Virtual Machine Manager", and instantly the MPEG-2 packet stream will start seeing continuity and stream errors.  The instant I close the "Virtual Machine Manager" and log out of X, everything returns to normal.

There's also a Dell PERC 5/i card (flashed to an LSI MegaRAID 8408E firmware) that's running 8-750GB drives in RAID-5 which is visible in dom0 as a file-server using samba.  And that's about it.

I'm not sure where to start looking in resolving this issue but issues of this type when searching other forums and answers seems to be PCI latency related and resetting them on certain PCI bus devices to fix continuity errors (even in a non-VM environment and straight up Windows-based OS).  Doing an lspci -vvv on dom0 under a Xen kernel, I noticed every single device on the PCI and PCIe has a latency set to 0 which I find very odd (or is that normal for native PCIe based chipsets?).  Also, I'm not even sure PCI latency affects PCIe devices as they do PCI devices (especially since the Q35 chipset is natively PCI-Express and all legacy PCI devices are being a PCIe-to-PCI bridge).  Or... am I just barking up the wrong tree? ;)

I can post a lspci -vvv if that would help.  Since the domU is HVM and it's Windows XP, I've tried using the "PCI Latency Tool 3.1.2" but the PCIe DVB-S card would not show in the list of PCI devices.  Other testing I've done, I started off using "ACPI Multiprocessor" as the HAL, then dropped to the more stable "Standard PC" HAL (so going back to the ACPI HAL means a re-install of the OS), and then disabling ACPI and APIC and turning off PAE... etc.  It has no affect.

Anyone have any ideas?  Thanks in advance!

-- 
Daniel Kao
Übermind, Inc.
Seattle, WA, U.S.A.

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