Re: [PATCH v2 2/2] Revert "xen-netback: Check for hotplug-status existence before watching"

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Tue, Feb 22, 2022 at 09:31:31AM +0100, Roger Pau Monné wrote:
> On Tue, Feb 22, 2022 at 01:18:17AM +0100, Marek Marczykowski-Górecki wrote:
> > This reverts commit 2afeec08ab5c86ae21952151f726bfe184f6b23d.
> > 
> > The reasoning in the commit was wrong - the code expected to setup the
> > watch even if 'hotplug-status' didn't exist. In fact, it relied on the
> > watch being fired the first time - to check if maybe 'hotplug-status' is
> > already set to 'connected'. Not registering a watch for non-existing
> > path (which is the case if hotplug script hasn't been executed yet),
> > made the backend not waiting for the hotplug script to execute. This in
> > turns, made the netfront think the interface is fully operational, while
> > in fact it was not (the vif interface on xen-netback side might not be
> > configured yet).
> > 
> > This was a workaround for 'hotplug-status' erroneously being removed.
> > But since that is reverted now, the workaround is not necessary either.
> > 
> > More discussion at
> > https://lore.kernel.org/xen-devel/afedd7cb-a291-e773-8b0d-4db9b291fa98@ipxe.org/T/#u
> > 
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> > ---
> > I believe this is the same issue as discussed at
> > https://lore.kernel.org/xen-devel/20220113111946.GA4133739@dingwall.me.uk/
> 
> Right - I believe we need to leave that workaround in place in libxl
> in order to deal with bogus Linux netbacks?

I'm afraid so, yes.

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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