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

[Pasi Kärkkäinen <pasik@xxxxxx>]

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?

If the PCI device in question has native flr capability, then native flr is 
used, right ? 
I guess I should read the full patch.. 

-- Pasi


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