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From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH] xen/x86: Remap text/data/bss with appropriate permissions
Date: Thu, 17 Mar 2016 09:32:58 -0600	[thread overview]
Message-ID: <56EADC3A02000078000DDF75@prv-mh.provo.novell.com> (raw)
In-Reply-To: <56EAC2E4.7040303@citrix.com>

>>> On 17.03.16 at 15:44, <andrew.cooper3@citrix.com> wrote:
> On 17/03/16 14:31, Jan Beulich wrote:
>> Also - do we really want to make this code dependent on
>> map_pages_to_xen() not intermediately zapping the mappings
>> being changed?
> 
> Do you mean "immediately"?

No.

> As far as I can tell, it is guaranteed to be safe, even when remapping
> the code section.  Updates to the live pagetables are using atomic
> writes, and I didn't spot a point which would end up with a transient
> non-present mapping.

But we may, at some point and for whatever reason, come to make
the function zap the mapping (i.e. clear the present bit), flush, and
only the re-establish the new mapping.

Jan


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  reply	other threads:[~2016-03-17 15:32 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-17 12:43 Andrew Cooper
2016-03-17 12:43 ` [PATCH] DO NOT APPLY - debug keys for inspecting Xen mappings Andrew Cooper
2016-03-17 14:31 ` [PATCH] xen/x86: Remap text/data/bss with appropriate permissions Jan Beulich
2016-03-17 14:44   ` Andrew Cooper
2016-03-17 15:32     ` Jan Beulich [this message]
2016-03-17 16:15       ` Andrew Cooper
2016-03-18  7:25         ` Jan Beulich
2016-03-18 19:49   ` [PATCH v2] " Andrew Cooper

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