Hi
I have been testing xen-unstable.hg (29/03/09) over the past
few days .. trying to enable passthrough for VGA.
I am using Debian 5.0 (lenny) x64 and compiling from source
each time. Tried both linux-2.6.18.8 and linux-2.6.27.5 from Xenbits …
Hardware is Nvidia Geforce 8800 512mb GTS PCIe on Intel X58
(ASUS P6T Deluxe) with Core i7 920 CPU.
(had to hack the xen/drviers/pci/passthrough/vtd/dmar.c
(line 388) and remove the DMAR bail because of bad RMRR tables.
I also have ATI X300 PCIe for Dom0 Console.
Using Xen parameter: iommu=passthrough,pv
Using Dom) parameter: pciback.hide=(‘…’)
I compiled pciback as embedded in the kernel and I have
tried many different scenarios:
1) Nvidia Primary (hidden with pciback.hide= kernel param)
(no ATI card installed)
2) ATI Primary, with Nvidia hidden (with pciback.hide=
kernel param)
3) all scenarios with pciback as module and using echo devn
> /sys/bus/pci/drivers/pciback/new_slot and bind
In all scenarios I can successfully see the correct PCI
device in the DomU(s), I have tried primarily Windows XP 32bit SP3 and also:
linux-2.6.18.8 and linux-2.6.27.5 PV and non PV kernels as DomU and (although I
didn’t load a driver) the lspci –vvv showed the devices.
Now, I progressed to installing drivers under the Win32 DomU
against the Nvidia card, windows correctly identified the device and installed
the driver! (latest from nvidia.com). As we all know – Windows wanted a
reboot- beforehand a quick check of the device and it has a Yellow exclamation
indicating reboot required and resources unavailable.
Reboot and XP starts up … BSOD .. nv4 driver fails .. L
Tried with the ATI X300 Primary (no NVidia connected) and
went through the same steps. Windows XP now boots without crash although the
ATI device still shows a yellow exclamation and insufficient resources.
To summarise, pciback functions as expected for PCIe in Dom0
and DomU sees the device. All tools work fine (xm pci-attach / pci-detach /
pci-list) and devid show and are managed correctly.
I have read all that there is on this subject and have come
to the conclusion that this is a problem with qemu-dm and the memory mapping
for the new Video device, the Cirrus or stdvga card is always present which I
believe may be causing the problem. I have tried nographics=1 but qemu-dm still
maps the Video BIOS.
Then I noticed that qemu-dm has the new options for
“-vga none” .. so I built a wrapper script for qemu-dm to launch
with this param. Unfortuntately the DomU doesn’t startup and the qemu log
does not show any mention of the Video memory ! so I believe the switch works,
but the DomU then fails to boot L
To solve this and make it usable I think some development of
qemu with regards to the Cirrus VGA and memory management when using more than
1 vga controller is necessary in order to remap the Cirrus or secondary vga
adapters in memory correctly. (its also difficult to configure a Windows
machine for a second vga when the primary is disabled lol.)
Also, I have run strace using a qemu-dm wrapper (very
verbose) and analysed the results –nothing seems obvious, but i`m not an
expert by far ….
Windows has been able to support multiple VGA cards for a
long time; I assume that MS is remapping these somehow?
I have read in 2 different places that this has worked for
others before (without the legacy patch for igfx) and with xen-unstable.hg ..
why does it not work for me ?
Any help / direction to further debug would be helpful .. I
think many people would like to get this one working once and for all!
Tim
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