From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Keir Fraser <keir@xen.org>
Subject: Re: [PATCH 3/3] domctl: pause vCPU for context reads
Date: Wed, 5 Feb 2014 15:43:34 +0000 [thread overview]
Message-ID: <52F25C26.10606@citrix.com> (raw)
In-Reply-To: <52F2695002000078001197AB@nat28.tlf.novell.com>
On 05/02/14 15:39, Jan Beulich wrote:
>>>> On 05.02.14 at 16:29, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>> On 05/02/14 14:54, Jan Beulich wrote:
>>> "Base" context reads already paused the subject vCPU when being the
>>> current one, but that special case isn't being properly dealt with
>>> anyway (at the very least when x86's fsgsbase feature is in use), so
>>> just disallow it.
>>>
>>> "Extended" context reads so far didn't do any pausing.
>>>
>>> While we can't avoid the reported data being stale by the time it
>>> arrives at the caller, this way we at least guarantee that it is
>>> consistent.
>>>
>>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>> Now I come to think about it, is this an ABI change, as we are now
>> disallowing a control domain to issue these hypercalls on itself?
> Of course it is, and intentionally so. As was patch 2. And imo it
> was never correct to allow this.
>
> Jan
>
It is certainly possible to get libxc to do this, but I would agree that
it has no valid use.
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
next prev parent reply other threads:[~2014-02-05 15:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-05 14:48 [PATCH 0/3] guest context management adjustments Jan Beulich
2014-02-05 14:52 ` [PATCH 1/3] x86: fix FS/GS base handling when using the fsgsbase feature Jan Beulich
2014-02-05 15:50 ` Andrew Cooper
2014-02-05 14:54 ` [PATCH 2/3] domctl: also pause domain for extended context updates Jan Beulich
2014-02-05 15:05 ` Andrew Cooper
2014-02-05 14:54 ` [PATCH 3/3] domctl: pause vCPU for context reads Jan Beulich
2014-02-05 15:29 ` Andrew Cooper
2014-02-05 15:39 ` Jan Beulich
2014-02-05 15:43 ` Andrew Cooper [this message]
2014-02-05 14:55 ` [PATCH 0/3] guest context management adjustments Jan Beulich
2014-02-05 16:02 ` George Dunlap
2014-02-05 15:35 ` Keir Fraser
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