Re: [PATCH] acpi: pcihp: make pending delete expire in 5sec

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Apr 04, 2023 at 01:06:38PM +0530, Ani Sinha wrote:
> 
> 
> On Tue, 4 Apr 2023, Gerd Hoffmann wrote:
> 
> >   Hi,
> >
> > > > Allowing pending delete expire brings ACPI PCI hotplug on par
> > > > with native PCIe unplug behavior [1] which in its turn refers
> > > > back to ACPI PCI hotplug ability to repeat unplug requests.
> >
> > > A bit concerned about how this interacts with failover,
> > > and 5sec is a lot of time that I hoped we'd avoid with acpi.
> > > Any better ideas of catching such misbehaving guests?
> >
> > The 5sec are coming from the pcie spec: The hot-unplug request can be
> > canceled within 5 seconds by pressing the button again. The problem here
> > is that both hotplug and hot-unplug use the same signaling path, so we
> > really have to wait the 5 seconds to avoid the OS mis-interpreting the
> > button press as 'cancel' event.
> >
> > ACPI hotplug hasn't this problem.  A unplug request is a unplug request,
> 
> For ACPI case, I think all we want is to make sure that the first unplug
> event to not stick forever. A non-zero but small delay would make sure
> that the first
> unplug event would get cleared after that interval and subsequent unplug
> events will get registered without that error.
> 
> > period.  And it can't be canceled.  So it should be possible to use a
> > shorter period.  Possibly even no delay at all.
> >
> > take care,
> >   Gerd
> >
> >


But why do we want a delay at all? for acpi you can resend
the interrupt as many times as you like.

-- 
MST