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RE: [Xen-users] Advantages of HVM vs. paravirtualization in aLinux-only

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Subject: RE: [Xen-users] Advantages of HVM vs. paravirtualization in aLinux-only enviroment?
From: "Jamie J. Begin" <begin@xxxxxxxxxxxxxxx>
Date: Mon, 28 Apr 2008 19:43:39 -0400
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>-----Original Message-----
>From: Ross S. W. Walker [mailto:rwalker@xxxxxxxxxxxxx] 
>Sent: Monday, April 28, 2008 1:53 PM
>To: Jamie J. Begin; xen-users@xxxxxxxxxxxxxxxxxxx
>Subject: RE: [Xen-users] Advantages of HVM vs. paravirtualization in
>aLinux-only enviroment?
>Jamie J. Begin wrote:
>> Newbie here... My hardware supports HVM (full virtualization), 
>> but I only need to run Linux on it.  I initially tried to 
>> create a HVM domU, but couldn't get pciback to work with a 
>> telephony card I need for use with Asterisk.  However 
>> everything seems to be working fine under a paravirtualized 
>> guest as long as I use permissive mode on the card. (Knock on 
>> wood-I've had some weird instability issues prior enabling 
>> permissive mode).  
>You can always look into the logs at the io port violations
>and add them to the pci-quirks for that card until you've
>covered them all. It's a little trial-and-error until you
>get them all covered, but it's more secure then just
>setting pci permissive globally.
>> Is there any real advantage to using HVM if I don't need to 
>> virtualize Windows?  And if there is, how do I go about 
>> passing through PCI cards to the HVM guest?  I'm trying to 
>> figure out if it's worth me continuing to hack on this problem.
>No, if your OS can do para-virtualized that is the preferred
>way to go. The only reason for HVM is if the OS cannot be

Thanks for the reply; at least I know I'm on the right track.  However, it
doesn't look like permissive mode actually solved my problem. 

When I try to reboot dom0, it switches to runlevel 6 and the xen init.d
script attempts to pause the Asterisk domU.  It's at that point I get an
"hda: interrupt lost" on the physical console. SSH become inaccessible and
eventually the system pukes up a bunch of ext3 and RAID controller related
errors and freezes.  I have to physically power cycle the box to get it back

Any suggestions?  This is a new Dell PowerEdge 1950 with a PERC SATA RAID 1
array, running CentOS 5.1 (2.6.18-53.1.14.el5xen) in both the dom0 and domU.
The PCI device that's being passed-through to the domU is a Digium AEX800
(which is actually a PCIe version of Digium's PCI-based TDM800P). lspci
output is:

0b:08.0 Ethernet controller: Digium, Inc. Unknown device 8002 (rev 11)
        Subsystem: Digium, Inc. Unknown device 8002
        Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B-
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort-
<TAbort- <MAbort- >SERR- <PERR-
        Interrupt: pin A routed to IRQ 16
        Region 0: I/O ports at dc00 [disabled] [size=256]
        Region 1: Memory at fc7dfc00 (32-bit, non-prefetchable) [disabled]
        Expansion ROM at fc7e0000 [disabled] [size=128K]
        Capabilities: [c0] Power Management version 2
                Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA
                Status: D0 PME-Enable- DSel=0 DScale=0 PME-

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