From mboxrd@z Thu Jan  1 00:00:00 1970
From: George Dunlap <george.dunlap@citrix.com>
Subject: Re: [PATCHv2 2/3] mm: don't free pages until mm locks
	are released
Date: Wed, 2 Dec 2015 16:30:41 +0000
Message-ID: <565F1CB1.7040909@citrix.com>
References: <1447440595-1151-1-git-send-email-david.vrabel@citrix.com>
	<1447440595-1151-3-git-send-email-david.vrabel@citrix.com>
	<AADFC41AFE54684AB9EE6CBC0274A5D15F729926@SHSMSX101.ccr.corp.intel.com>
	<20151202162329.GA94392@deinos.phlegethon.org>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta3.messagelabs.com ([195.245.230.39])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <prvs=771036ecc=George.Dunlap@citrix.com>)
	id 1a4AIp-0006Hr-Sv
	for xen-devel@lists.xenproject.org; Wed, 02 Dec 2015 16:30:48 +0000
In-Reply-To: <20151202162329.GA94392@deinos.phlegethon.org>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Tim Deegan <tim@xen.org>, "Tian, Kevin" <kevin.tian@intel.com>
Cc: "Nakajima, Jun" <jun.nakajima@intel.com>, George Dunlap <george.dunlap@eu.citrix.com>, Andrew Cooper <andrew.cooper3@citrix.com>, David Vrabel <david.vrabel@citrix.com>, Jan Beulich <jbeulich@suse.com>, "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
List-Id: xen-devel@lists.xenproject.org

On 02/12/15 16:23, Tim Deegan wrote:
> At 07:25 +0000 on 02 Dec (1449041100), Tian, Kevin wrote:
>>> From: David Vrabel [mailto:david.vrabel@citrix.com]
>>> Sent: Saturday, November 14, 2015 2:50 AM
>>>
>>> If a page is freed without translations being invalidated, and the page is
>>> subsequently allocated to another domain, a guest with a cached
>>> translation will still be able to access the page.
>>>
>>> Currently translations are invalidated before releasing the page ref, but
>>> while still holding the mm locks.  To allow translations to be invalidated
>>> without holding the mm locks, we need to keep a reference to the page
>>> for a bit longer in some cases.
>>>
>>> [ This seems difficult to a) verify as correct; and b) difficult to get
>>> correct in the future.  A better suggestion would be useful.  Perhaps
>>> using something like pg->tlbflush_needed mechanism that already exists
>>> for pages from PV guests? ]
>>
>> Per-page flag looks clean in general, but not an expert here. Tim might
>> have a better idea.
> 
> I think you can probably use the tlbflush_timestamp stuff as-is for
> EPT flushes -- the existing TLB shootdowns already drop all EPT
> translations.

Are you saying that if you do a TLB shootdown you don't need to do an
invept command?  That doesn't sound right.

 -George