Re: Passthrough of 2 PCI devices works 80% (Kernel 2.6.37, Debian Squeeze, Win7 VM)

[Da Powah <dapowah@hotmail.com>]

> > i`ve got a question about pci passthrogh of 2 pci devices (2x DVB-S2
> > PCI cards with Saa7146 PCI Bridge from Technotrend: S2-3200). 
> > 
> > I am using squeeze with a 2.6.37 selfcompiled Kernel. I want to
> > passthrough both devices to a virtual machine (Win7) an get problems.
> > If i passthrough one device (other is unplugged) it works flawlessly. 
> 
> I'm glad to hear it works one at a time.  It's oddly specific that you
> mention it works if the other card is unplugged, can you only physically
> have one card plugged in at a time for it to work (ie. if you have both
> cards physically installed, but only one assigned to the guest, does it
> work)?  Can you simultaneously assign each card to separate guests and
> they work?
I tried both devices, one at a time. Both are working well.
KVM supports the passthrough with all devices together behind a bridge only. So
i have to pass all 03.0x.y devices through to one guest only.


> > The time i add both devices and pass them through i am still able to
> > start the VM and i don`t see anything in the error logs. Even Windows7
> > or XP detects both cards and installs the driver correctly (actual BDA
> > Driver, standard broadcast video driver). But the time i want to acces
> > the cards, i get a BSOD - caused by the driver.
> 
> I'll toss out a dumb question, can the drivers for Win7 or WinXP drive
> two cards when running on bare metal?  Does a Linux guest work with both
> cards better?
The driver support more than one devices. I already contacted the support and
they assured me, that the driver i used is working. Using both cards in Linux
won`t help, because i want to use them with a windows application.

> > I already aligned the io memory of both devices, checked the libvirt
> > logs, kernel and syslogs - there is nothing for a kvm newbe that seems
> > to be odd. The kernel is compiled with all the mentioned kernel
> > options of the linux-kvm.org page - except that i compiled the stub
> > driver as module. One card alone (both tried separately) is working
> > w/o any flaws. Kvm is able to pass through all devices behind a PCI
> > Bridge - so take a look at the 03:0x.0 devices below: i use those 2
> > sat boards only in 3 PCI slots.
> > 
> > What am i able to do to make deeper analysis or to solve the
> > problem ? 
> 
> If each card works when assigned separately and you can boot the guest
> with both cards assign and the drivers load and device manager isn't
> reporting any errors, I'd lean towards a Windows driver issue.  There is
> some debugging you can enable in hw/device-assignment.c that might shed
> some light on what the drivers is trying to do before the BSOD.  What
> error is the BSOD reporting?  Are you using the latest qemu-kvm.git?
The drivers work on 'bare metal' as you mentioned above. I won`t believe that
its a pure driver-only issue for now. But the other behavior of the passed
through device may cause the driver fault. The BSOD tells, that it is a general
driver issue which caused the fault.
I am using the kvm codse which is distributed in the kernel 2.6.37 and standard
debian squeeze repositories for installation of the tools lib-virt, etc...

I am trying to get some more PCI spcecific data from the windows guests. I will
try to use both cards in a linux vm.

> Thanks,
> 
> Alex

Thanks for participating in my very special problem, 

DP