On 2012-09-17 21:15, Konrad Rzeszutek Wilk wrote:
On Mon, Sep 17, 2012 at 01:42:54PM +0100, Ian Campbell wrote:
On Mon, 2012-09-17 at 13:32 +0100, Pasi Kärkkäinen wrote:
On Mon, Sep 17, 2012 at 01:51:03PM +0200, Robin Axelsson wrote:
There is one thing I wonder though when it comes to PCI passthrough:

Can Xen reset hardware through the d3d0 in the ACPI interface and/or
through a 'bus reset' or a 'link reset'? Or can it reset hardware
that is marked for passthrough only through FLR?

For details see e.g.

I added xen-devel to the CC-list.
Hopefully someone there can reply this question.
With a pvops dom0 Xen resets devices by writing to its "reset" node in
sysfs so it will reset the device using whatever method the dom0 kernel
supports for that device.
And if you use Xen PCI-back it has this enabled so you don't even
need the 'reset' functionality.
The version of Linux I have to hand has, in __pci_dev_reset, calls to
the following in this order and stops after the first one which
       * pci_dev_specific_reset (AKA per device quirks)
       * pcie_flr
       * pci_af_flr
       * pci_pm_reset
       * pci_parent_bus_reset

See drivers/pci/pci.c in the kernel for more info.

IIRC classic Xen kernels had similar code in pciback, although I don't
know which specific sets of actions or in which order they were tried.


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That sounds like great news, that means that FLR is not a requirement to successfully pass through hardware without errors, as is stated in the VTdHowTo page. So it seems that the VTdHowTo page needs to be updated with this information.

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