PCI passthrough problem

PCI passthrough problem

[Phil (list)]

If this isn't the right place to ask, any pointers to the correct place
are appreciated...

I'm trying to see if I can get PCI passthrough working for a video
capture card (Hauppauge Colossus 1x PCIe) under a Windows XP guest (32
-bit).  Things appear to be somewhat working (Windows is seeing the
device, the drivers successfully installed, and device manager
indicates everything is working) however when I fire up the capture
application, it is not able to find the device despite Windows
recognizing it (no errors, it just doesn't 'see' any installed capture
devices).  There is also a secondary capture/viewer application that
won't even install due to not being able to find a capture card.  Since
that wasn't the behavior when running it natively under Windows, I'm
assuming that the issue is related to PCI passthrough but it's
difficult to be certain since I'm not seeing any errors beyond the
capture applications not being able to find the device.

Some details on my setup: i7-2600 running on a Q77 motherboard with VT
-d enabled in bios.  I'm running Debian Linux (testing) with qemu-kvm
1:2.4+dfsg-3 and am passing intel_iommu=on as a kernel parameter on
boot.  These are the main details I can think of to share, but if there
is any additional info that would be useful, please let me know and
I'll be happy to provide it.

Having read through a few different posts around the 'net on how to do
PCI passthrough (pretty much everything I've found was discussing GPUs,
and almost always on a different distro), the only thing that jumps out
as a potential problem is that the card in question does not appear to
support FLR.  However, I'm not clear if that's an absolute requirement
for PCI passthrough or something that is specific to GPU support? 
 Beyond that, I'm at a loss as to what the issue could be...

Thanks,
Phil

Re: PCI passthrough problem

[Mauricio Tavares]

On Thu, Oct 1, 2015 at 3:27 AM, Phil (list) <pbpublist@gmail.com> wrote:
> If this isn't the right place to ask, any pointers to the correct place
> are appreciated...
>
> I'm trying to see if I can get PCI passthrough working for a video
> capture card (Hauppauge Colossus 1x PCIe) under a Windows XP guest (32
> -bit).  Things appear to be somewhat working (Windows is seeing the
> device, the drivers successfully installed, and device manager
> indicates everything is working) however when I fire up the capture
> application, it is not able to find the device despite Windows
> recognizing it (no errors, it just doesn't 'see' any installed capture
> devices).  There is also a secondary capture/viewer application that
> won't even install due to not being able to find a capture card.  Since
> that wasn't the behavior when running it natively under Windows, I'm
> assuming that the issue is related to PCI passthrough but it's
> difficult to be certain since I'm not seeing any errors beyond the
> capture applications not being able to find the device.
>
      I think you need to find out if the problem follows the program,
the card, or the passthrough thingie. For instance, is there any other
program you can run to see if it sees the card? If you can't think of
anything, you could run a, say, ubuntu/fedora livecd (start you vm
client and tell it to boot from iso) and see if it can see and use the
card.

> Some details on my setup: i7-2600 running on a Q77 motherboard with VT
> -d enabled in bios.  I'm running Debian Linux (testing) with qemu-kvm
> 1:2.4+dfsg-3 and am passing intel_iommu=on as a kernel parameter on
> boot.  These are the main details I can think of to share, but if there
> is any additional info that would be useful, please let me know and
> I'll be happy to provide it.
>
> Having read through a few different posts around the 'net on how to do
> PCI passthrough (pretty much everything I've found was discussing GPUs,
> and almost always on a different distro), the only thing that jumps out
> as a potential problem is that the card in question does not appear to
> support FLR.  However, I'm not clear if that's an absolute requirement
> for PCI passthrough or something that is specific to GPU support?
>  Beyond that, I'm at a loss as to what the issue could be...
>
> Thanks,
> Phil
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: PCI passthrough problem

[Phil (list)]

On Thu, 2015-10-01 at 08:32 -0400, Mauricio Tavares wrote:
> On Thu, Oct 1, 2015 at 3:27 AM, Phil (list) <pbpublist@gmail.com>
> wrote:
> > If this isn't the right place to ask, any pointers to the correct
> > place
> > are appreciated...
> > 
> > I'm trying to see if I can get PCI passthrough working for a video
> > capture card (Hauppauge Colossus 1x PCIe) under a Windows XP guest
> > (32
> > -bit).  Things appear to be somewhat working (Windows is seeing the
> > device, the drivers successfully installed, and device manager
> > indicates everything is working) however when I fire up the capture
> > application, it is not able to find the device despite Windows
> > recognizing it (no errors, it just doesn't 'see' any installed
> > capture
> > devices).  There is also a secondary capture/viewer application
> > that
> > won't even install due to not being able to find a capture card. 
> >  Since
> > that wasn't the behavior when running it natively under Windows,
> > I'm
> > assuming that the issue is related to PCI passthrough but it's
> > difficult to be certain since I'm not seeing any errors beyond the
> > capture applications not being able to find the device.
> > 
>       I think you need to find out if the problem follows the
> program,
> the card, or the passthrough thingie. For instance, is there any
> other
> program you can run to see if it sees the card? If you can't think of
> anything, you could run a, say, ubuntu/fedora livecd (start you vm
> client and tell it to boot from iso) and see if it can see and use
> the
> card.
> 

I only have the two capture apps that came with the card as I don't
really use Windows for much other than this card anymore.

To try to verify that everything is fine from a hardware / Windows
driver standpoint: I took a spare drive and performed a bare metal Win
XP install, installed the drivers, and then the capture software (i.e.
the same sequence and software versions as I used in the VM) and
everything works properly (i.e. both capture applications were able to
detect and use the capture card as expected).   Other than using a
different hard drive, all other system hardware was identical.  So that
would seem to rule out everything from the hardware through to the
Windows applications and leave it back in the realm of kvm/PCI
passthrough.

Unfortunately, no Linux drivers exist for this card (i.e. the reason
I'm attempting to use it under Windows in a VM) so any other Linux
distro would have about the same level of support in that it would
recognize that the PCI card exists but then not be able to do anything
with it.  If you're thinking that there is a problem with version of
kvm in Debian, I would be open to trying another distro if that would
help troubleshoot it.  I'm also reasonably comfortable navigating
around kvm, it's the PCI passthrough functionality that is new to me.

> > Some details on my setup: i7-2600 running on a Q77 motherboard with
> > VT
> > -d enabled in bios.  I'm running Debian Linux (testing) with qemu
> > -kvm
> > 1:2.4+dfsg-3 and am passing intel_iommu=on as a kernel parameter on
> > boot.  These are the main details I can think of to share, but if
> > there
> > is any additional info that would be useful, please let me know and
> > I'll be happy to provide it.
> > 
> > Having read through a few different posts around the 'net on how to
> > do
> > PCI passthrough (pretty much everything I've found was discussing
> > GPUs,
> > and almost always on a different distro), the only thing that jumps
> > out
> > as a potential problem is that the card in question does not appear
> > to
> > support FLR.  However, I'm not clear if that's an absolute
> > requirement
> > for PCI passthrough or something that is specific to GPU support?
> >  Beyond that, I'm at a loss as to what the issue could be...
> > 
> > Thanks,
> > Phil
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: PCI passthrough problem

[Alex Williamson]

On Thu, 2015-10-01 at 22:38 -0400, Phil (list) wrote:
> On Thu, 2015-10-01 at 08:32 -0400, Mauricio Tavares wrote:
> > On Thu, Oct 1, 2015 at 3:27 AM, Phil (list) <pbpublist@gmail.com>
> > wrote:
> > > If this isn't the right place to ask, any pointers to the correct
> > > place
> > > are appreciated...
> > > 
> > > I'm trying to see if I can get PCI passthrough working for a video
> > > capture card (Hauppauge Colossus 1x PCIe) under a Windows XP guest
> > > (32
> > > -bit).  Things appear to be somewhat working (Windows is seeing the
> > > device, the drivers successfully installed, and device manager
> > > indicates everything is working) however when I fire up the capture
> > > application, it is not able to find the device despite Windows
> > > recognizing it (no errors, it just doesn't 'see' any installed
> > > capture
> > > devices).  There is also a secondary capture/viewer application
> > > that
> > > won't even install due to not being able to find a capture card. 
> > >  Since
> > > that wasn't the behavior when running it natively under Windows,
> > > I'm
> > > assuming that the issue is related to PCI passthrough but it's
> > > difficult to be certain since I'm not seeing any errors beyond the
> > > capture applications not being able to find the device.
> > > 
> >       I think you need to find out if the problem follows the
> > program,
> > the card, or the passthrough thingie. For instance, is there any
> > other
> > program you can run to see if it sees the card? If you can't think of
> > anything, you could run a, say, ubuntu/fedora livecd (start you vm
> > client and tell it to boot from iso) and see if it can see and use
> > the
> > card.
> > 
> 
> I only have the two capture apps that came with the card as I don't
> really use Windows for much other than this card anymore.
> 
> To try to verify that everything is fine from a hardware / Windows
> driver standpoint: I took a spare drive and performed a bare metal Win
> XP install, installed the drivers, and then the capture software (i.e.
> the same sequence and software versions as I used in the VM) and
> everything works properly (i.e. both capture applications were able to
> detect and use the capture card as expected).   Other than using a
> different hard drive, all other system hardware was identical.  So that
> would seem to rule out everything from the hardware through to the
> Windows applications and leave it back in the realm of kvm/PCI
> passthrough.
> 
> Unfortunately, no Linux drivers exist for this card (i.e. the reason
> I'm attempting to use it under Windows in a VM) so any other Linux
> distro would have about the same level of support in that it would
> recognize that the PCI card exists but then not be able to do anything
> with it.  If you're thinking that there is a problem with version of
> kvm in Debian, I would be open to trying another distro if that would
> help troubleshoot it.  I'm also reasonably comfortable navigating
> around kvm, it's the PCI passthrough functionality that is new to me.

Are you using vfio to do the device assignment or legacy KVM device
assignment.  If the latter, try the former.  Since you're using a 32-bit
Windows guest, what CPU model are you exposing to the VM?  Windows can
be rather particular about enabling MSI for devices if the processor
model seen by the VM is too old (does the device support MSI?).  '-cpu
host' might help or "host-passthrough" if using libvirt.  You can look
in /proc/interrupts on the host and see if you're getting interrupts
(non-zero count on at least one of the CPUs for the interrupt associated
with the device).  If instead the device is using INTx interrupts,
interrupt masking might be broken.  You can try using the nointxmask=1
module option to vfio-pci, for force masking at the APIC rather than the
device, but be forewarned that you'll need to make the interrupt for the
device exclusive, either by locating it in a slot where it won't share
interrupts or unloading drivers from devices sharing the interrupt line.

There's always the chance that the device is simply not compatible with
PCI device assignment.  We do rely on some degree of good behavior on
the part of the device.  Some environments also expect to find the
device behind a PCIe root port, which is not the topology we expose on
the default 440fx VM chipset.  It's possible that such devices might
work on the Q35 chipset or by placing the device behind a pci-bridge to
fool the software.  It's really hard to tell what might be wrong,
especially since the driver appears to work and only the application
fails, and it's all proprietary code within the black box of a VM.
Thanks,

Alex

Re: PCI passthrough problem

[Phil (list)]

On Thu, 2015-10-01 at 21:00 -0600, Alex Williamson wrote:
> On Thu, 2015-10-01 at 22:38 -0400, Phil (list) wrote:
> > On Thu, 2015-10-01 at 08:32 -0400, Mauricio Tavares wrote:
> > > On Thu, Oct 1, 2015 at 3:27 AM, Phil (list) <pbpublist@gmail.com>
> > > wrote:
> > > > If this isn't the right place to ask, any pointers to the
> > > > correct
> > > > place
> > > > are appreciated...
> > > > 
> > > > I'm trying to see if I can get PCI passthrough working for a
> > > > video
> > > > capture card (Hauppauge Colossus 1x PCIe) under a Windows XP
> > > > guest
> > > > (32
> > > > -bit).  Things appear to be somewhat working (Windows is seeing
> > > > the
> > > > device, the drivers successfully installed, and device manager
> > > > indicates everything is working) however when I fire up the
> > > > capture
> > > > application, it is not able to find the device despite Windows
> > > > recognizing it (no errors, it just doesn't 'see' any installed
> > > > capture
> > > > devices).  There is also a secondary capture/viewer application
> > > > that
> > > > won't even install due to not being able to find a capture
> > > > card. 
> > > >  Since
> > > > that wasn't the behavior when running it natively under
> > > > Windows,
> > > > I'm
> > > > assuming that the issue is related to PCI passthrough but it's
> > > > difficult to be certain since I'm not seeing any errors beyond
> > > > the
> > > > capture applications not being able to find the device.
> > > > 
> > >       I think you need to find out if the problem follows the
> > > program,
> > > the card, or the passthrough thingie. For instance, is there any
> > > other
> > > program you can run to see if it sees the card? If you can't
> > > think of
> > > anything, you could run a, say, ubuntu/fedora livecd (start you
> > > vm
> > > client and tell it to boot from iso) and see if it can see and
> > > use
> > > the
> > > card.
> > > 
> > 
> > I only have the two capture apps that came with the card as I don't
> > really use Windows for much other than this card anymore.
> > 
> > To try to verify that everything is fine from a hardware / Windows
> > driver standpoint: I took a spare drive and performed a bare metal
> > Win
> > XP install, installed the drivers, and then the capture software
> > (i.e.
> > the same sequence and software versions as I used in the VM) and
> > everything works properly (i.e. both capture applications were able
> > to
> > detect and use the capture card as expected).   Other than using a
> > different hard drive, all other system hardware was identical.  So
> > that
> > would seem to rule out everything from the hardware through to the
> > Windows applications and leave it back in the realm of kvm/PCI
> > passthrough.
> > 
> > Unfortunately, no Linux drivers exist for this card (i.e. the
> > reason
> > I'm attempting to use it under Windows in a VM) so any other Linux
> > distro would have about the same level of support in that it would
> > recognize that the PCI card exists but then not be able to do
> > anything
> > with it.  If you're thinking that there is a problem with version
> > of
> > kvm in Debian, I would be open to trying another distro if that
> > would
> > help troubleshoot it.  I'm also reasonably comfortable navigating
> > around kvm, it's the PCI passthrough functionality that is new to
> > me.
> 
> Are you using vfio to do the device assignment or legacy KVM device
> assignment.  If the latter, try the former.

vfio

>   Since you're using a 32-bit
> Windows guest, what CPU model are you exposing to the VM?  Windows
> can
> be rather particular about enabling MSI for devices if the processor
> model seen by the VM is too old (does the device support MSI?).  '
> -cpu
> host' might help or "host-passthrough" if using libvirt.

I am passing through the host CPU (Sandy Bridge... which is about a
decade newer than Win XP though.)  If I'm reading the lspci output
correctly, the card supports MSI but it is not enabled (which seems to
make sense as your comment indicates that this would be something that
Windows, not Linux, would enable?):

02:00.0 Multimedia controller: ViXS Systems, Inc. Device 3000
	Subsystem: Hauppauge computer works Inc. Device d180
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0, Cache Line Size: 32 bytes
	Interrupt: pin A routed to IRQ 16
	Region 0: Memory at f2100000 (64-bit, prefetchable) [size=1M]
	Region 2: Memory at f7100000 (32-bit, non-prefetchable)
[size=64K]
	Capabilities: [40] Power Management version 3
		Flags: PMEClk- DSI- D1+ D2- AuxCurrent=375mA
PME(D0+,D1+,D2-,D3hot+,D3cold-)
		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit+
		Address: 0000000000000000  Data: 0000
	Capabilities: [70] Express (v2) Endpoint, MSI 00
		DevCap:	MaxPayload 128 bytes, PhantFunc 0,
Latency L0s <256ns, L1 <16us
			ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset-
		DevCtl:	Report errors: Correctable- Non-Fatal-
Fatal- Unsupported-
			RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
			MaxPayload 128 bytes, MaxReadReq 512 bytes
		DevSta:	CorrErr- UncorrErr- FatalErr- UnsuppReq-
AuxPwr- TransPend-
		LnkCap:	Port #0, Speed 2.5GT/s, Width x1, ASPM
L0s L1, Exit Latency L0s <256ns, L1 <16us
			ClockPM+ Surprise- LLActRep- BwNot- ASPMOptComp
-
		LnkCtl:	ASPM Disabled; RCB 64 bytes Disabled-
CommClk+
			ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
		LnkSta:	Speed 2.5GT/s, Width x1, TrErr- Train-
SlotClk+ DLActive- BWMgmt- ABWMgmt-
		DevCap2: Completion Timeout: Not Supported,
TimeoutDis+, LTR-, OBFF Not Supported
		DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-,
LTR-, OBFF Disabled
		LnkCtl2: Target Link Speed: 2.5GT/s, EnterCompliance-
SpeedDis-
			 Transmit Margin: Normal Operating Range,
EnterModifiedCompliance- ComplianceSOS-
			 Compliance De-emphasis: -6dB
		LnkSta2: Current De-emphasis Level: -6dB,
EqualizationComplete-, EqualizationPhase1-
			 EqualizationPhase2-, EqualizationPhase3-,
LinkEqualizationRequest-
	Capabilities: [100 v1] Advanced Error Reporting
		UESta:	DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt-
UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
		UEMsk:	DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt-
UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
		UESvrt:	DLP+ SDES+ TLP- FCP+ CmpltTO- CmpltAbrt-
UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol-
		CESta:	RxErr- BadTLP- BadDLLP- Rollover- Timeout
- NonFatalErr-
		CEMsk:	RxErr- BadTLP- BadDLLP- Rollover- Timeout
- NonFatalErr+
		AERCap:	First Error Pointer: 00, GenCap+ CGenEn-
ChkCap+ ChkEn-
	Capabilities: [140 v1] Virtual Channel
		Caps:	LPEVC=0 RefClk=100ns PATEntryBits=1
		Arb:	Fixed- WRR32- WRR64- WRR128-
		Ctrl:	ArbSelect=Fixed
		Status:	InProgress-
		VC0:	Caps:	PATOffset=00 MaxTimeSlots=1
RejSnoopTrans-
			Arb:	Fixed- WRR32- WRR64- WRR128-
TWRR128- WRR256-
			Ctrl:	Enable+ ID=0 ArbSelect=Fixed
TC/VC=01
			Status:	NegoPending- InProgress-
	Kernel driver in use: vfio-pci

>   You can look
> in /proc/interrupts on the host and see if you're getting interrupts
> (non-zero count on at least one of the CPUs for the interrupt
> associated
> with the device).

It appears to be getting interrupts but I assume there's no way to tell
which device (usb1 or vfio-intx) they are from:
 16:        654      
 6309          0          0          0          0          0          0
  IR-IO-APIC  16-fasteoi   ehci_hcd:usb1, vfio-intx(0000:02:00.0)

>   If instead the device is using INTx interrupts,
> interrupt masking might be broken.

Am I correct in interpreting  this statement along with the above
output to mean that it's using INTx interrupts?

>   You can try using the nointxmask=1
> module option to vfio-pci, for force masking at the APIC rather than
> the
> device, but be forewarned that you'll need to make the interrupt for
> the
> device exclusive, either by locating it in a slot where it won't
> share
> interrupts or unloading drivers from devices sharing the interrupt
> line.
> 

Given the above, it appears to be sharing the interrupt with one of the
USB controllers.  If your advice still stands, I can swap a couple of
cards and see if I can get an exclusive interrupt or try to get
everything off of that USB controller so that I can disable it.  I'd
appreciate your thoughts on if I would be better off trying this or
your next suggestion first...

> There's always the chance that the device is simply not compatible
> with
> PCI device assignment.  We do rely on some degree of good behavior on
> the part of the device.  Some environments also expect to find the
> device behind a PCIe root port, which is not the topology we expose
> on
> the default 440fx VM chipset.  It's possible that such devices might
> work on the Q35 chipset or by placing the device behind a pci-bridge
> to
> fool the software.

After doing a bit of reading up on 440fx vs Q35, this looks promising:
since this is a PCIe card, the Q35 chipset seems likely to be needed. 
 The only question I have is how to get Win XP to install using it. (on
newer machines you need to set the bios to legacy/emulation mode in a
couple of places and I'm not sure yet how / if there's a way to 'fake
it' for Windows with Q35)  Are you aware of any docs / posts that deal
with this scenario?

>   It's really hard to tell what might be wrong,
> especially since the driver appears to work and only the application
> fails, and it's all proprietary code within the black box of a VM.


One additional detail I've found on closer examination: it appears that
the driver installation did not complete fully in the VM, Windows just
thinks it did.  On the bare metal installation, there are two installed
device drivers: one for the capture device (which doesn't have any
hardware resources listed), one for the encoder (which does list
hardware resources)... but both functions are performed on the card (it
captures an audio/video input and then hardware encodes it to either
mpeg 2 or h.264) so the first driver is not just a pseudo/software
driver.  In the VM, only the encoder is being installed.  This explains
a lot re: why the capture applications are having problems seeing the
card.  Is it possible that there's some unreported hardware resource
that needs to be passed through that isn't being identified as a result
of seeing it as a PCI rather than a PCIe device?  (I'm thinking it
could be something along the lines of the PCIe extended configuration
space)

> Thanks,
> 
> Alex
> 

Thank you,
Phil

PCI Passthrough Problem

[Aaron Clausen]

I'm trying once again to get PCI passthrough working (KVM 84 on Ubuntu
9.10), and I'm getting this error :

LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
/usr/bin/kvm -S -M pc-0.11 -m 4096 -smp 4 -name mailserver -uuid
76a83471-e94a-3658-fa61-8eceaa74ffc2 -monitor
unix:/var/run/libvirt/qemu/mailserver.monitor,server,nowait -localtime
-boot c -drive file=,if=ide,media=cdrom,index=2 -drive
file=/var/lib/libvirt/images/mailserver.img,if=virtio,index=0,boot=on
-drive file=/var/lib/libvirt/images/mailserver-2.img,if=virtio,index=1
-net nic,macaddr=54:52:00:1b:b2:56,vlan=0,model=virtio,name=virtio.0
-net tap,fd=17,vlan=0,name=tap.0 -serial pty -parallel none -usb
-usbdevice tablet -vnc 127.0.0.1:0 -k en-us -vga cirrus -pcidevice
host=0a:01.0
char device redirected to /dev/pts/0
get_real_device: /sys/bus/pci/devices/0000:0a:01.0/config: Permission denied
init_assigned_device: Error: Couldn't get real device (0a:01.0)!
Failed to initialize assigned device host=0a:01.0

Any thoughts?

-- 
Aaron Clausen
mightymartianca@gmail.com

Re: PCI Passthrough Problem

[Yolkfull Chow]

On Thu, Jan 21, 2010 at 09:24:36PM -0800, Aaron Clausen wrote:
> I'm trying once again to get PCI passthrough working (KVM 84 on Ubuntu
> 9.10), and I'm getting this error :
> 
> LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
> /usr/bin/kvm -S -M pc-0.11 -m 4096 -smp 4 -name mailserver -uuid
> 76a83471-e94a-3658-fa61-8eceaa74ffc2 -monitor
> unix:/var/run/libvirt/qemu/mailserver.monitor,server,nowait -localtime
> -boot c -drive file=,if=ide,media=cdrom,index=2 -drive
> file=/var/lib/libvirt/images/mailserver.img,if=virtio,index=0,boot=on
> -drive file=/var/lib/libvirt/images/mailserver-2.img,if=virtio,index=1
> -net nic,macaddr=54:52:00:1b:b2:56,vlan=0,model=virtio,name=virtio.0
> -net tap,fd=17,vlan=0,name=tap.0 -serial pty -parallel none -usb
> -usbdevice tablet -vnc 127.0.0.1:0 -k en-us -vga cirrus -pcidevice
> host=0a:01.0
> char device redirected to /dev/pts/0
> get_real_device: /sys/bus/pci/devices/0000:0a:01.0/config: Permission denied
> init_assigned_device: Error: Couldn't get real device (0a:01.0)!
> Failed to initialize assigned device host=0a:01.0

Seems libvirt initialize the PCI devices problem, you could manually unbind this 
device from host kernel driver and try above command again.

For unbind this device please refer to :

http://www.linux-kvm.org/page/How_to_assign_devices_with_VT-d_in_KVM

> 
> Any thoughts?
> 
> -- 
> Aaron Clausen
> mightymartianca@gmail.com
> --
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