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

[Govinda Tatti <govinda.tatti@xxxxxxxxxx>]

Thanks Pasi for your response. Please see below for my comments.

On 11/8/2017 11:38 AM, Pasi Kärkkäinen wrote:
> Hi,
>
> On Wed, Nov 08, 2017 at 09:44:48AM -0600, Govinda Tatti wrote:
> > Thanks Jan for your review comments. Please see below for my comments.
> >
> > On 11/7/2017 8:40 AM, Jan Beulich wrote:
> > > > > > On 06.11.17 at 18:48, <Govinda.Tatti@xxxxxxxxxx> wrote:
> > > > --- a/Documentation/ABI/testing/sysfs-driver-pciback
> > > > +++ b/Documentation/ABI/testing/sysfs-driver-pciback
> > > > @@ -11,3 +11,15 @@ Description:
> > > >                   #echo 00:19.0-E0:2:FF > /sys/bus/pci/drivers/pciback/quirks
> > > >                   will allow the guest to read and write to the configuration
> > > >                   register 0x0E.
> > > > +
> > > > +What:           /sys/bus/pci/drivers/pciback/do_flr
> > > > +Date:           Nov 2017
> > > > +KernelVersion:  4.15
> > > > +Contact:        xen-devel@xxxxxxxxxxxxxxxxxxxx
> > > > +Description:
> > > > +                An option to perform a slot or bus reset when a PCI device
> > > > +               is owned by Xen PCI backend. Writing a string of DDDD:BB:DD.F
> > > > +               will cause the pciback driver to perform a slot or bus reset
> > > > +               if the device supports it. It also checks to make sure that
> > > > +               all of the devices under the bridge are owned by Xen PCI
> > > > +               backend.
> > > Why do you name this "do_flr" when you don't even try FLR, but
> > > go to slot or then bus reset right away.
> > Yes, I agree but xen toolstack has already been modified to consume"do_flr"
> > attribute. Hence, we are using the
> > function that matches with sysfs attribute.
> Hmm.. I remember some discussion from ages ago related to this.
>
> Back then it was suggested to "emulate" the flr capability (by doing slot or 
> bus reset) for devices which don't have *native* flr available? So is this patch perhaps 
> related to that?
I don't think so but either Konrad or someone can comment on it.
> If the PCI device in question has native flr capability, then native flr is 
> used, right ?
Yes.
> I guess I should read the full patch..
Please check it and let us know your comments.

Cheers
GOVINDA

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