Re: Xen PCI passthru supported reset methods (d3d0, FLR, bus reset, link reset)

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

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.
> > > http://www.vmware.com/files/pdf/techpaper/vsp_4_vmdirectpath_host.pdf
> > >
> > 
> > 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
> succeeds:
>       * 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.
> 
> Ian.
> 
> 
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