From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Deegan Subject: Re: [PATCH 1 of 7] Make p2m lookups fully synchronized wrt modifications Date: Fri, 10 Feb 2012 15:33:59 +0000 Message-ID: <20120210153359.GA32107@ocelot.phlegethon.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Andres Lagar-Cavilla Cc: george.dunlap@eu.citrix.com, andres@gridcentric.ca, xen-devel@lists.xensource.com, keir.xen@gmail.com, adin@gridcentric.ca List-Id: xen-devel@lists.xenproject.org At 00:45 -0500 on 09 Feb (1328748346), Andres Lagar-Cavilla wrote: > We achieve this by locking/unlocking the global p2m_lock in get/put_gfn. > > The lock is always taken recursively, as there are many paths that > call get_gfn, and later, make another attempt at grabbing the p2m_lock. > > The lock is not taken for shadow lookups. We believe there are no problems > remaining for synchronized p2m+shadow paging, but we are not enabling this > combination due to lack of testing. Unlocked shadow p2m access are tolerable as > long as shadows do not gain support for paging or sharing. > > HAP (EPT) lookups and all modifications do take the lock. > > Signed-off-by: Andres Lagar-Cavilla Acked-by: Tim Deegan