Issues with getting PCI pass-through to work

Issues with getting PCI pass-through to work

[Adhyas Avasthi]

I have a PCI WLAN controller that I wish to pass-through to the
standard linux-img VM (downloaded from qemu website).
When I try "qemu-kvm -pcidevice host=0c:00.0,name=abcd linux-0.2.img"
The VM does boot up but does not see the device.

On the command prompt, I see the following message:
Failed to assign irq for "abcd": Operation not supported
Perhaps you are assigning a device that shares an IRQ with another device?

I want to know what does this message exactly mean? Is PCI
pass-through having the requirement of reconfiguring the IRQ of my
host devices before I can pass them through? Can I configure qemu-kvm
somehow to emulate the IRQ (and other registers) instead of trying to
pass-through the IRQ etc?

BTW, my box has VT and VT-d enabled in BIOS.

--
Adhyas
********************************************************************
Two types have compatible type if their types are the same.
   — ANSI C Standard, 3.1.2.6.
********************************************************************

Re: Issues with getting PCI pass-through to work

[Adhyas Avasthi]

Tried working on it a bit more. Now it complains that it cannot find IOMMU.
This is an Intel Montevina chipset with DMA remapping support (VT-d).
Any pointers as to why it is not finding the support?
The message is coming from hw/device-assignment.c after the call to
kvm_check_extension for IOMMU fails.
The corresponding ioctl code in kvm-kmod lands in iommu_found(), which
I believe is reporting false.

I am wondering if kvm-kmod driver has support for Intel VT-d (Intel
Cantiga chipsets etc) ? Can PCI pass-through work without IOMMU?

Thanks,
Adhyas


On Sun, May 30, 2010 at 6:19 PM, Adhyas Avasthi <adhyas@gmail.com> wrote:
> I have a PCI WLAN controller that I wish to pass-through to the
> standard linux-img VM (downloaded from qemu website).
> When I try "qemu-kvm -pcidevice host=0c:00.0,name=abcd linux-0.2.img"
> The VM does boot up but does not see the device.
>
> On the command prompt, I see the following message:
> Failed to assign irq for "abcd": Operation not supported
> Perhaps you are assigning a device that shares an IRQ with another device?
>
> I want to know what does this message exactly mean? Is PCI
> pass-through having the requirement of reconfiguring the IRQ of my
> host devices before I can pass them through? Can I configure qemu-kvm
> somehow to emulate the IRQ (and other registers) instead of trying to
> pass-through the IRQ etc?
>
> BTW, my box has VT and VT-d enabled in BIOS.
>
> --
> Adhyas
> ********************************************************************
> Two types have compatible type if their types are the same.
>    — ANSI C Standard, 3.1.2.6.
> ********************************************************************
>



-- 
Adhyas
********************************************************************
Two types have compatible type if their types are the same.
    — ANSI C Standard, 3.1.2.6.
********************************************************************