linux-kernel - RE: [Xen-devel] [PATCH 2/4] xenbus: limit when state is forced to closed

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Message-ID: <3412e42d13224b6786613e58dc189ebf@EX13D32EUC003.ant.amazon.com>
Date:   Mon, 9 Dec 2019 12:03:54 +0000
From:   "Durrant, Paul" <pdurrant@...zon.com>
To:     Jürgen Groß <jgross@...e.com>,
        Roger Pau Monné <roger.pau@...rix.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "Stefano Stabellini" <sstabellini@...nel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: RE: [Xen-devel] [PATCH 2/4] xenbus: limit when state is forced to
 closed

> -----Original Message-----
> From: Jürgen Groß <jgross@...e.com>
> Sent: 09 December 2019 11:55
> To: Roger Pau Monné <roger.pau@...rix.com>; Durrant, Paul
> <pdurrant@...zon.com>
> Cc: linux-kernel@...r.kernel.org; xen-devel@...ts.xenproject.org; Stefano
> Stabellini <sstabellini@...nel.org>; Boris Ostrovsky
> <boris.ostrovsky@...cle.com>
> Subject: Re: [Xen-devel] [PATCH 2/4] xenbus: limit when state is forced to
> closed
> 
> On 09.12.19 12:39, Roger Pau Monné wrote:
> > On Thu, Dec 05, 2019 at 02:01:21PM +0000, Paul Durrant wrote:
> >> Only force state to closed in the case when the toolstack may need to
> >> clean up. This can be detected by checking whether the state in
> xenstore
> >> has been set to closing prior to device removal.
> >
> > I'm not sure I see the point of this, I would expect that a failure to
> > probe or the removal of the device would leave the xenbus state as
> > closed, which is consistent with the actual driver state.
> >
> > Can you explain what's the benefit of leaving a device without a
> > driver in such unknown state?
> 
> And more concerning: did you check that no frontend/backend is
> relying on the closed state to be visible without closing having been
> set before?

Blkfront doesn't seem to mind and I believe the Windows PV drivers cope, but I don't really understand the comment since this patch is actually removing a case where the backend transitions directly to closed.

  Paul

> 
> 
> Juergen