From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCHv2 2/3] mm: don't free pages until mm locks are released Date: Mon, 30 Nov 2015 14:10:06 +0000 Message-ID: <565C58BE.406@citrix.com> References: <1447440595-1151-1-git-send-email-david.vrabel@citrix.com> <1447440595-1151-3-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1a3P9g-0004x4-9b for xen-devel@lists.xenproject.org; Mon, 30 Nov 2015 14:10:12 +0000 In-Reply-To: <1447440595-1151-3-git-send-email-david.vrabel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: David Vrabel , xen-devel@lists.xenproject.org Cc: Kevin Tian , Jun Nakajima , George Dunlap , Andrew Cooper , Tim Deegan , Jan Beulich List-Id: xen-devel@lists.xenproject.org On 13/11/15 18:49, David Vrabel wrote: > 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? ] ping? This question is quite important and hasn't been answered yet. David