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Tue, 7 May 2019 03:10:07 GMT Received: from ca-dmjordan1.us.oracle.com (/10.211.9.48) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 06 May 2019 20:10:06 -0700 Date: Mon, 6 May 2019 23:09:57 -0400 From: Daniel Jordan To: Jason Gunthorpe Cc: Daniel Jordan , "akpm@linux-foundation.org" , Alan Tull , Alexey Kardashevskiy , Alex Williamson , Benjamin Herrenschmidt , Christoph Lameter , Christophe Leroy , Davidlohr Bueso , Mark Rutland , Michael Ellerman , Moritz Fischer , Paul Mackerras , Steve Sistare , Wu Hao , "linux-mm@kvack.org" , "kvm@vger.kernel.org" , "kvm-ppc@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-fpga@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] mm: add account_locked_vm utility function Message-ID: <20190507030957.3qp7yflco6ckcj5q@ca-dmjordan1.us.oracle.com> References: <20190503201629.20512-1-daniel.m.jordan@oracle.com> <20190503232818.GA5182@mellanox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190503232818.GA5182@mellanox.com> User-Agent: NeoMutt/20180323-268-5a959c X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9249 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905070018 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9249 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905070018 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, May 03, 2019 at 11:28:22PM +0000, Jason Gunthorpe wrote: > On Fri, May 03, 2019 at 01:16:30PM -0700, Daniel Jordan wrote: > > Andrew, this one patch replaces these six from [1]: > > > > mm-change-locked_vms-type-from-unsigned-long-to-atomic64_t.patch > > vfio-type1-drop-mmap_sem-now-that-locked_vm-is-atomic.patch > > vfio-spapr_tce-drop-mmap_sem-now-that-locked_vm-is-atomic.patch > > fpga-dlf-afu-drop-mmap_sem-now-that-locked_vm-is-atomic.patch > > kvm-book3s-drop-mmap_sem-now-that-locked_vm-is-atomic.patch > > powerpc-mmu-drop-mmap_sem-now-that-locked_vm-is-atomic.patch > > > > That series converts locked_vm to an atomic, but on closer inspection causes at > > least one accounting race in mremap, and fixing it just for this type > > conversion came with too much ugly in the core mm to justify, especially when > > the right long-term fix is making these drivers use pinned_vm instead. > > Did we ever decide what to do here? Should all these drivers be > switched to pinned_vm anyhow? Well, there were the concerns about switching in [1]. Alex, is there an example of an application or library that would break or be exploitable? If there were particular worries (qemu for vfio type1, for example), perhaps some coordinated changes across the kernel and userspace would be possible, especially given the amount of effort it's likely going to take to get the locked_vm/pinned_vm accounting sorted out. [1] https://lore.kernel.org/linux-mm/20190213130330.76ef1987@w520.home/