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

[Govinda Tatti <Govinda.Tatti@xxxxxxxxxx>]

Jan,

Do you have any further comments on the current version of this patch?. 
Otherwise, I will work on the review comments and publish next version 
of this patch later this week. Please let me know. Thanks.
Cheers
GOVINDA
On 12/1/2017 10:16 AM, Govinda Tatti wrote:
> On 11/30/2017 8:46 AM, Jan Beulich wrote:
> > > > > On 30.11.17 at 15:15, <govinda.tatti@xxxxxxxxxx> wrote:
> > > 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).
> > Is that true even for root complex integrated end points? A
> > random system's lspci output doesn't seem to agree with what
> > you say. A typical example would be USB controllers all sitting
> > on bus 0, but having different slot numbers. You clearly won't
> > be able to ever bus-reset these, and if you checked all devices
> > on bus 0 you would then also not be able to slot-reset them.
> Here, slot reset refers to any PCIe slot that implements or supports
> hotplug feature. The slot reset ultimately invokes "pciehp_reset_slot()".
> W.r.t integrated endpoints, these can be reset either through FLR or
> secondary bus reset methods only.
>
> Cheers
> GOVINDA
>
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