Re: [Xen-devel] Xen PCI passthru supported reset methods (d3d0, FLR, bus reset, link reset)

[Robin Axelsson <gu99roax@xxxxxxxxxxxxxxxxxxx>]

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.
> > > > 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.
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
> .
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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