Re: [Xen-users] XEN 4.6 / 4.9 - PCI-Passthrough USB 3.0 win7 / Win10 not working

[Håkon Alstadheim <hakon@xxxxxxxxxxxxxxxxxx>]

Den 03. jan. 2018 02:06, skrev Chuck Ritola:
> On Tue, Jan 2, 2018 at 6:43 AM, Xen Mann <xensemann@xxxxxx> wrote:
[...]

>>> For 16.04 and winXP this is working great! The PCIe Card appears in
>>> Windows device manager, the attached USB-Device shows up in the device
>>> manager and works like a charm.
>>>
>>> However, this is not possible for my system with win7 and Win10 and the
>>> very same setup.
[...]

>> -> Why is passthrough of USB-PCI-Cards working for XP and Ubuntu 16.04,
>> even if those USB-Cards do not support FLReset.
> 
> ... The lack of function-level-reset support does not guarantee
> failure of passthrough, though it often can introduce undefined
> behavior when multiple domUs use the device consecutively. These clear
> after the host is reset. From what I've seen, most devices do not
> support FLReset but many will pass-through and be usable.
> 
> It would be good practice to ensure dom0 binds pciback to the
> passed-through devices on boot so it does not initialize the devices
> prematurely. Else, they may be in an intolerable state when the domU
> OS tries to initialize them.
> 

Bios & Firmware will (at least partly) initialize USB-cards to allow
usb-keyboards to work during boot, so hiding the card from dom0 might
not help that much.

I'm not a programmer so what follows is to be taken with a grain of salt.


I believe there is a handoff protocol between bios and dom0 that means
dom0 will manage. This MIGHT mean that domUs will not be so fortunate.
All this might be affected by various bios settings (something like
legacy int<whatever> among other things) . So tinkering might let you
muddle through, and then an update or the phase of the moon will mess
you up again.

I have similar problems on my system, and I have been wondering if going
full UEFI on both the hardware and the domUs might help.

I have not been able to try out that theory, since I am having trouble
booting using <code>bios = "ovmf"</code> . I have been able to boot
domUs using ovmf on occasion, but even then dumU boot hangs for several
minutes, probably looking for floppies or something. Long story, qemu
fixes are in the works I belive.

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