From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefano Stabellini Subject: Re: [PATCH 0/3] make ballooned out pages have a valid mapping at all times Date: Mon, 22 Jul 2013 16:35:30 +0100 Message-ID: References: <51ED1A36.10200@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51ED1A36.10200@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 Cc: xen-devel@lists.xensource.com, Ian Campbell , Stefano Stabellini , alex@alex.org.uk, dcrisan@flexiant.com List-Id: xen-devel@lists.xenproject.org On Mon, 22 Jul 2013, David Vrabel wrote: > On 21/07/13 18:32, Stefano Stabellini wrote: > > Hi all, > > this patch series limits problems caused by tcp retransmits on NFS when > > the original block pages were mapped from a foreign domain and now the > > mapping is gone. > > > > It accomplishes the goal by: > > > > 1) mapping all ballooned out pages to a "balloon_trade_page"; > > 2) making sure that once a grant is unmapped, the original mapping to > > balloon_trade_page is restored atomically. > > I think this can be fixed without any hypervisor-side changes, although > hypervisor changes will allow you to do it more efficiently. > > Use a per-CPU set of trade pages. > > Note MFN of this CPU's trade page (trade_mfn). > Do the grant_unmap_and_replace(), (trade page mapping's MFN is cleared > but this is ok as nothing is accessing the page via this mapping). > update_va_mapping on trade page VA to set its MFN to trade_mfn. I am going to go for this, avoiding any Xen side changes.