linux-kernel - Re: [Xen-devel] [PATCH V2] Xen/pciback: Implement PCI slot or bus reset with 'do

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Date:   Thu, 30 Nov 2017 01:27:49 -0700
From:   "Jan Beulich" <JBeulich@...e.com>
To:     "Govinda Tatti" <govinda.tatti@...cle.com>
Cc:     <roger.pau@...rix.com>, <xen-devel@...ts.xenproject.org>,
        <boris.ostrovsky@...cle.com>, "Juergen Gross" <jgross@...e.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH V2] Xen/pciback: Implement PCI slot or
 bus reset with 'do_flr' SysFS attribute

>>> On 29.11.17 at 18:38, <govinda.tatti@...cle.com> 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.

Jan