Re: [Xen-devel] [PATCH V2] Xen/pciback: Implement PCI slot or bus reset with 'do_flr' SysFS attribute

[Govinda Tatti]

On 11/30/2017 2:27 AM, Jan Beulich wrote:
> > > > On 29.11.17 at 18:38, <govinda.tatti@xxxxxxxxxx> wrote:
> > > > In the case of bus or slot reset, our goal is to reset connected PCIe
> > > > fabric/card/endpoint.
> > > > The connected card/endpoint can be multi-function device. So, same
> > > > walk-through and checking
> > > > is needed irrespective of type of reset being used.
> > > I don't follow: The scope of other devices/functions possibly
> > > affected by a reset depends on the type of reset, doesn't it?
> > For PCIe platforms, both slot and bus reset endup resetting all connected
> > device/functions on thesecondary bus (behind the root-port or
> > downstream-port).
> According to my understanding this contradicts the comment
> ahead of pci_reset_slot(), which talks of multiple slots per bus.
> In such a setup, I can't see why resetting on slot would affect
> other slots on the same bus. At the same time the comment
> says that the slot reset may resolve to a bus one when there's
> just a single slot on the bus.
For legacy PCI/PCI-X, we can have multiple slots per bus but not with 
PCI-Express
(each link will be on a separate bus). In anycase, we need to 
walk-through other
device/functions on the same bus/slot and check their status before 
using slot/bus
reset.

Cheers
GOVINDA