From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out1-smtp.messagingengine.com ([66.111.4.25]:57381 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751336AbdJCIz5 (ORCPT ); Tue, 3 Oct 2017 04:55:57 -0400 Date: Tue, 3 Oct 2017 10:56:06 +0200 From: Greg KH To: Andrew Donnellan Cc: stable@vger.kernel.org, fbarrat@linux.vnet.ibm.com, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 4.4] cxl: Fix driver use count Message-ID: <20171003085606.GF15659@kroah.com> References: <20170927004317.9671-1-andrew.donnellan@au1.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170927004317.9671-1-andrew.donnellan@au1.ibm.com> Sender: stable-owner@vger.kernel.org List-ID: On Wed, Sep 27, 2017 at 10:43:17AM +1000, Andrew Donnellan wrote: > From: Frederic Barrat > > commit 197267d0356004a31c4d6b6336598f5dff3301e1 upstream. > > cxl keeps a driver use count, which is used with the hash memory model > on p8 to know when to upgrade local TLBIs to global and to trigger > callbacks to manage the MMU for PSL8. > > If a process opens a context and closes without attaching or fails the > attachment, the driver use count is never decremented. As a > consequence, TLB invalidations remain global, even if there are no > active cxl contexts. > > We should increment the driver use count when the process is attaching > to the cxl adapter, and not on open. It's not needed before the > adapter starts using the context and the use count is decremented on > the detach path, so it makes more sense. > > It affects only the user api. The kernel api is already doing The > Right Thing. > > Signed-off-by: Frederic Barrat > Cc: stable@vger.kernel.org # v4.2+ > Fixes: 7bb5d91a4dda ("cxl: Rework context lifetimes") > Acked-by: Andrew Donnellan > Signed-off-by: Michael Ellerman > [ajd: backport to stable v4.4 tree] > Signed-off-by: Andrew Donnellan Thanks for this and the 4.9 backport. greg k-h