From: Dan Magenheimer <dan.magenheimer@oracle.com>
To: Jan Beulich <JBeulich@novell.com>
Cc: JeremyFitzhardinge <jeremy@goop.org>,
"Xen-Devel (xen-devel@lists.xensource.com)"
<xen-devel@lists.xensource.com>,
tmem-devel@oss.oracle.com, Kurt Hackel <kurt.hackel@oracle.com>,
Vasiliy G Tolstov <v.tolstov@selfip.ru>,
Keir Fraser <keir.fraser@eu.citrix.com>,
stephen.spector@citrix.com, Chris Mason <chris.mason@oracle.com>
Subject: RE: [RFC] tmem ABI change... backwards compatibility unnecessary?
Date: Thu, 2 Sep 2010 16:19:52 -0700 (PDT) [thread overview]
Message-ID: <c84f89c9-34ae-4599-9f1e-90ed84dfa837@default> (raw)
In-Reply-To: <4C7E87970200007800013C2C@vpn.id2.novell.com>
> From: Jan Beulich [mailto:JBeulich@novell.com]
> Sent: Wednesday, September 01, 2010 9:04 AM
> To: Dan Magenheimer
> Cc: stephen.spector@citrix.com; Keir Fraser; JeremyFitzhardinge; Xen-
> Devel (xen-devel@lists.xensource.com); Chris Mason; Kurt Hackel; tmem-
> devel@oss.oracle.com; Vasiliy G Tolstov
> Subject: Re: [RFC] tmem ABI change... backwards compatibility
> unnecessary?
>
> >>> On 01.09.10 at 16:36, Dan Magenheimer <dan.magenheimer@oracle.com>
> wrote:
> > I *think* it is still the case that tmem is experimental
> > and is not used anywhere yet in production. If I am
> > wrong, PLEASE LET ME KNOW ASAP.
>
> Well, if you call us shipping it (default disabled) in a couple of
> releases "not used in production"...
>
> > I am inclined to update the Xen tmem implementation
> > to only support v1 and gracefully fail v0.
>
> If "graceful" really means what it says, this would appear to be
> acceptable irrespective of my note above.
OK, I will submit a patch tomorrow with the following characteristics:
v0 (current) hypervisor + v0 guest: succeeds
v1 (patched) hypervisor + v1 guest: succeeds
v0 (current) hypervisor + v1 guest: fails
v1 (patched) hypervisor + v0 guest: fails
where fails is an xm dmesg message that says "unsupported
spec version" when the guest attempts to create a pool.
And pool creation failure ensures that all further tmem
operations also fail (indeed never even result in a
hypercall for most tmem-enabled kernels).
Thank goodness ABI versioning was built into tmem from
the beginning!
Dan
next prev parent reply other threads:[~2010-09-02 23:19 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-01 14:36 [RFC] tmem ABI change... backwards compatibility unnecessary? Dan Magenheimer
2010-09-01 14:44 ` Vasiliy G Tolstov
2010-09-01 15:37 ` Dan Magenheimer
2010-09-01 15:04 ` Jan Beulich
2010-09-02 23:19 ` Dan Magenheimer [this message]
2010-09-02 23:39 ` Jeremy Fitzhardinge
2010-09-03 14:47 ` Dan Magenheimer
2010-09-01 16:46 ` Jeremy Fitzhardinge
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