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Tue, 22 Mar 2022 08:29:26 -0700 (PDT) Received: from redhat.com ([38.15.36.239]) by smtp.gmail.com with ESMTPSA id i11-20020a056e021b0b00b002c83d5df5a2sm1727094ilv.81.2022.03.22.08.29.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Mar 2022 08:29:25 -0700 (PDT) Date: Tue, 22 Mar 2022 09:29:23 -0600 From: Alex Williamson To: Jason Gunthorpe Subject: Re: [PATCH RFC 04/12] kernel/user: Allow user::locked_vm to be usable for iommufd Message-ID: <20220322092923.5bc79861.alex.williamson@redhat.com> In-Reply-To: <20220322145741.GH11336@nvidia.com> References: <4-v1-e79cd8d168e8+6-iommufd_jgg@nvidia.com> <808a871b3918dc067031085de3e8af6b49c6ef89.camel@linux.ibm.com> <20220322145741.GH11336@nvidia.com> Organization: Red Hat MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=alex.williamson@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Cc: Jean-Philippe Brucker , Chaitanya Kulkarni , kvm@vger.kernel.org, Niklas Schnelle , Jason Wang , Cornelia Huck , Kevin Tian , Daniel Jordan , iommu@lists.linux-foundation.org, "Michael S. Tsirkin" , Joao Martins , David Gibson X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Tue, 22 Mar 2022 11:57:41 -0300 Jason Gunthorpe wrote: > On Tue, Mar 22, 2022 at 03:28:22PM +0100, Niklas Schnelle wrote: > > On Fri, 2022-03-18 at 14:27 -0300, Jason Gunthorpe wrote: > > > > > > user->locked_vm is the correct accounting to use for ulimit because it is > > > per-user, and the ulimit is not supposed to be per-process. Other > > > places (vfio, vdpa and infiniband) have used mm->pinned_vm and/or > > > mm->locked_vm for accounting pinned pages, but this is only per-process > > > and inconsistent with the majority of the kernel. > > > > Since this will replace parts of vfio this difference seems > > significant. Can you explain this a bit more? > > I'm not sure what to say more, this is the correct way to account for > this. It is natural to see it is right because the ulimit is supposted > to be global to the user, not effectively reset every time the user > creates a new process. > > So checking the ulimit against a per-process variable in the mm_struct > doesn't make too much sense. I'm still picking my way through the series, but the later compat interface doesn't mention this difference as an outstanding issue. Doesn't this difference need to be accounted in how libvirt manages VM resource limits? AIUI libvirt uses some form of prlimit(2) to set process locked memory limits. A compat interface might be an interesting feature, but does it only provide ioctl compatibility and not resource ulimit compatibility? Thanks, Alex _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu