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From: George Dunlap <George.Dunlap@citrix.com>
To: Ian Jackson <Ian.Jackson@citrix.com>
Cc: Anthony Perard <anthony.perard@citrix.com>,
	xen-devel <xen-devel@lists.xenproject.org>,
	Wei Liu <wei.liu2@citrix.com>
Subject: Re: [PATCH 4/9] dm_depriv: Describe expected usage of device_model_user parameter
Date: Wed, 28 Nov 2018 17:27:04 +0000	[thread overview]
Message-ID: <456DCBF9-87F6-44E0-8110-987F526C2DB3@citrix.com> (raw)
In-Reply-To: <23550.50187.383519.177147@mariner.uk.xensource.com>



> On Nov 28, 2018, at 4:36 PM, Ian Jackson <ian.jackson@citrix.com> wrote:
> 
> George Dunlap writes ("[PATCH 4/9] dm_depriv: Describe expected usage of device_model_user parameter"):
>> A number of subsequent patches rely on as-yet undefined behavior for
>> what the `device_model_user` parameter does.  Rather than implement it
>> incorrectly (or randomly), or remove the feature, describe an expected
>> usage for the feature.  Further patches will make decisions based on
>> this expected usage.
> 
> This document seems to document a fine feature.  I don't mind the docs
> patch being separate but I don't know why you wouldn't add it in the
> same patch as you implement it.

Because the feature is already implemented and working correctly according to the pre-series semantics (AFAICT), but not documented (other than a comment in libxl_types.idl saying, “is not ready for use yet” (which I suppose I should remove while I’m at it)).

When I came to implement kill-by-uid, I came upon the questions: If device_model_user is specified, should I attempt to kill by uid or not?  And, is device_model_user allowed to be “root”?

If we expect device_model_user not to be shared with any other domains, then we can (and probably should) kill by uid; and of course the uid must not be root.  If we expect device_model_user to be shared with other domains, then we cannot kill by uid, and we might consider allowing the uid to be root.

I found no guidance in the code one way or the other; so this change is proposal of what I think is the most useful behavior: Namely, that we make the semantics “must be unique per domain”, rather than “may be shared”.

Given that...

> So, I guess,
> 
> Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

Does the Ack still stand?

 -George

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  reply	other threads:[~2018-11-28 17:27 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-23 17:14 [PATCH 1/9] libxl: Remove redundant pidpath setting George Dunlap
2018-11-23 17:14 ` [PATCH 2/9] libxl: Move dm user determination logic into a helper function George Dunlap
2018-11-28 15:20   ` Wei Liu
2018-11-28 16:33   ` Ian Jackson
2018-11-30 12:46   ` George Dunlap
2018-11-23 17:14 ` [PATCH 3/9] libxl: Get rid of support for QEMU_USER_BASE (xen-qemuuser-domidNN) George Dunlap
2018-11-28 15:32   ` Wei Liu
2018-11-30 12:53     ` George Dunlap
2018-11-30 16:56       ` Wei Liu
2018-11-28 16:34   ` Ian Jackson
2018-11-28 17:02     ` George Dunlap
2018-11-29 12:19       ` Ian Jackson
2018-11-23 17:14 ` [PATCH 4/9] dm_depriv: Describe expected usage of device_model_user parameter George Dunlap
2018-11-28 15:37   ` Wei Liu
2018-11-28 16:36   ` Ian Jackson
2018-11-28 17:27     ` George Dunlap [this message]
2018-11-29 12:20       ` Ian Jackson
2018-11-23 17:14 ` [PATCH 5/9] libxl: Do root checks once in libxl__domain_get_device_model_uid George Dunlap
2018-11-28 16:39   ` Ian Jackson
2018-11-28 17:38     ` George Dunlap
2018-11-29 17:09       ` Ian Jackson
2018-11-29 17:43         ` George Dunlap
2018-11-23 17:14 ` [PATCH 6/9] libxl: Move qmp cleanup into devicemodel destroy function George Dunlap
2018-11-28 16:39   ` Ian Jackson
2018-11-23 17:15 ` [PATCH 7/9] libxl: Make killing of device model asynchronous George Dunlap
2018-11-28 16:43   ` Ian Jackson
2018-11-30 16:12     ` George Dunlap
2018-11-30 16:14       ` George Dunlap
2018-11-30 16:22         ` Ian Jackson
2018-11-30 16:22       ` Ian Jackson
2018-11-23 17:15 ` [PATCH 8/9] libxl: Kill QEMU by uid when possible George Dunlap
2018-11-23 17:18   ` George Dunlap
2018-11-28 15:57     ` Anthony PERARD
2018-11-29 11:55       ` Wei Liu
2018-11-29 12:00         ` George Dunlap
2018-11-29 12:26           ` Ian Jackson
2018-11-29 12:38             ` George Dunlap
2018-11-29 17:16               ` Ian Jackson
2018-11-28 16:56   ` Ian Jackson
2018-11-28 17:55     ` George Dunlap
2018-11-29 17:01       ` Ian Jackson
2018-11-30 16:37     ` George Dunlap
2018-11-23 17:15 ` [PATCH 9/9] libxl: Kill QEMU with "reaper" ruid George Dunlap
2018-11-28 17:02   ` Ian Jackson
2018-11-28 18:33     ` George Dunlap
2018-11-29 11:39       ` George Dunlap
2018-11-29 17:15       ` Ian Jackson
2018-11-28 15:20 ` [PATCH 1/9] libxl: Remove redundant pidpath setting Wei Liu
2018-11-28 16:25 ` Ian Jackson

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