Xen users - Sep 2008 - pci passthrough question. Do I need VT-D ?

Hi,

I really need help.  I spent 2 days already on this pci passthrough thing.

I''m using Xen 3.2.1 with Centos 5.2 64 bits on intel VT.  I''d
like to
use PCI passthrough and I don''t think I need VT-D functionality.

I''m trying to pass PCI 12:01.0 to my domU guest.
I got this error when I use "xm create /etc/xen/hvm_centos_2.cfg"

Using config file "/etc/xen/hvm_centos_2.cfg".
Error: Fail to assign device(12:1.0): maybe VT-d is not enabled, or
the device is not exist, or it has already been assigned to other
domain

I thought that I can do PCI-passthrough w/o VT-D.
Do I misunderstand anything ?   How do I solve this problems ?

Here is some debugging info:

I managed to use pciback module to hide
my device (qlogic).  Here is the output from dmesg.

ACPI: PCI interrupt for device 0000:12:01.0 disabled
pciback 0000:12:01.0: seizing device
PCI: Enabling device 0000:12:01.0 (0150 -> 0153)
ACPI: PCI Interrupt 0000:12:01.0[A] -> GSI 25 (level, low) -> IRQ 21
ACPI: PCI interrupt for device 0000:12:01.0 disabled
ACPI: PCI interrupt for device 0000:12:01.1 disabled
pciback 0000:12:01.1: seizing device
PCI: Enabling device 0000:12:01.1 (0150 -> 0153)
ACPI: PCI Interrupt 0000:12:01.1[B] -> GSI 24 (level, low) -> IRQ 22
ACPI: PCI interrupt for device 0000:12:01.1 disabled

I also noticed that cat /proc/cpuinfo does not show vmx flag to
indicate vt.  I checked bios of HP proliant DL380 and made sure that
VT was enabled.

flags           : fpu de tsc msr pae cx8 apic sep mtrr cmov pat
clflush acpi mmx fxsr sse sse2 ss ht syscall lm constant_tsc pni cx16
lahf_lm

Thanks,
-- 
-Nick K

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I know very little about this, but if I remember correctly,
searching the archives will show you that VT-D  is certainly required for
PCI passthrough to HVM domUs (maybe not for PV ones, but I''m not so
sure on
that).  You might try creating a PV domU to do this in, or it might be
quicker to search the archives in case that''s not possible either.
	Dustin

-----Original Message-----
From: xen-users-bounces@lists.xensource.com
[mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Nick S
Kanakakorn
Sent: Tuesday, September 09, 2008 02:42
To: xen-users@lists.xensource.com
Subject: [Xen-users] pci passthrough question. Do I need VT-D ?

Hi,

I really need help.  I spent 2 days already on this pci passthrough thing.

I''m using Xen 3.2.1 with Centos 5.2 64 bits on intel VT.  I''d
like to
use PCI passthrough and I don''t think I need VT-D functionality.

I''m trying to pass PCI 12:01.0 to my domU guest.
I got this error when I use "xm create /etc/xen/hvm_centos_2.cfg"

Using config file "/etc/xen/hvm_centos_2.cfg".
Error: Fail to assign device(12:1.0): maybe VT-d is not enabled, or
the device is not exist, or it has already been assigned to other
domain

I thought that I can do PCI-passthrough w/o VT-D.
Do I misunderstand anything ?   How do I solve this problems ?

Here is some debugging info:

I managed to use pciback module to hide
my device (qlogic).  Here is the output from dmesg.

ACPI: PCI interrupt for device 0000:12:01.0 disabled
pciback 0000:12:01.0: seizing device
PCI: Enabling device 0000:12:01.0 (0150 -> 0153)
ACPI: PCI Interrupt 0000:12:01.0[A] -> GSI 25 (level, low) -> IRQ 21
ACPI: PCI interrupt for device 0000:12:01.0 disabled
ACPI: PCI interrupt for device 0000:12:01.1 disabled
pciback 0000:12:01.1: seizing device
PCI: Enabling device 0000:12:01.1 (0150 -> 0153)
ACPI: PCI Interrupt 0000:12:01.1[B] -> GSI 24 (level, low) -> IRQ 22
ACPI: PCI interrupt for device 0000:12:01.1 disabled

I also noticed that cat /proc/cpuinfo does not show vmx flag to
indicate vt.  I checked bios of HP proliant DL380 and made sure that
VT was enabled.

flags           : fpu de tsc msr pae cx8 apic sep mtrr cmov pat
clflush acpi mmx fxsr sse sse2 ss ht syscall lm constant_tsc pni cx16
lahf_lm

Thanks,
-- 
-Nick K

_______________________________________________
Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users



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indeed, VT-d is needed to do pci passthrough to a HVM domain.
It is not needed for a PV domain, i have been running a mythtv domU with
multiple TV-cards for ages.

but there are some requirements to get this to work.
make sure that :
- you do not load any drivers for the device on dom0 (google "pciback"
for
more info)
- your domU has enough memory (pci cards do use memory) and not too much,
trial and error is the way to go.
- you domU kernels support PCI and the device that you''re trying to
passthrough
- you add the "pci" statement to your config file (ex: pci
[''04:08.0''],[''04:09.0''],[''06:09.0'']
)
- if problems arise, you probably need to append a statement like this one
to the kernel options of the domU:
      "iommu=soft swiotlb=force"
- one more caveat: some PCI cards actually are more then 1 pci device in the
output of lspci.
  for example a tvcard with seperate audio device -> you need to passthrough
them both
  other devices are not "dividable" for example my new quad port
gigabit
card is actually 4 pci devices, but i have to passthrough them 2 by 2

i have this working for tvcards, network cards, a scsi card and USB as well
as serial.
but all for PV domains, i haven''t tested yet with my new VT-d enabled
mobo,
that should be able to do this in HVM domains as well.

Greetings,
Sven


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