linux-kernel - Re: [Xen-devel] [PATCH 1/2] xen: wrap xenbus on xenfs with COMPAT option

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Message-ID: <565DA473.9030000@cardoe.com>
Date:	Tue, 1 Dec 2015 07:45:23 -0600
From:	Doug Goldstein <cardoe@...doe.com>
To:	David Vrabel <david.vrabel@...rix.com>,
	linux-kernel@...r.kernel.org
Cc:	xen-devel@...ts.xenproject.org,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [Xen-devel] [PATCH 1/2] xen: wrap xenbus on xenfs with COMPAT
 option

On 12/1/15 4:44 AM, David Vrabel wrote:
> On 01/12/15 10:42, David Vrabel wrote:
>> On 30/11/15 21:35, Doug Goldstein wrote:
>>> Since Xen 4.6.0, using xenbus via xenfs (/proc/xen/xenbus) is deprecated
>>> and /dev/xen/xenbus via pvops is used instead. This is an effort to
>>> eventually drop this interface after a reasonable amount of time.
>>
>> I would prefer the ... /proc/xen/evtchn files to be
> 
> I meant /proc/xen/privcmd here.
> 
> David
> 

I can look into that. I do have a few questions, some of which are out
of scope from the original patch.

Would it be preferable to just remove "xenbus" from the xenfs
filesystem? Ever since Linux 3.14 even if you are running a version of
Xen earlier than 4.6 you will not be able to have a disaggregated
xenstore (which is the xenbus consumer) due to the addition of F_ATOMIC_POS.

Is it safe for a kernel virtual filesystem to provide a symlink outside
of itself where the destination can't be verified? Its possible this
already exists and I just don't know off any cases off the top of my head.

Since the /proc/xen mount point has been marked as COMPAT for nearly 6
years would the eventual goal be to move xenfs to somewhere like
/sys/hypervisor given that most of the virtual filesystems are mounted
under /sys now days?

-- 
Doug Goldstein

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