From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9F11BC433EF for ; Thu, 2 Jun 2022 16:31:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237067AbiFBQbH (ORCPT ); Thu, 2 Jun 2022 12:31:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237058AbiFBQbH (ORCPT ); Thu, 2 Jun 2022 12:31:07 -0400 Received: from mail-qt1-x835.google.com (mail-qt1-x835.google.com [IPv6:2607:f8b0:4864:20::835]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9405A2AD994 for ; Thu, 2 Jun 2022 09:31:01 -0700 (PDT) Received: by mail-qt1-x835.google.com with SMTP id ew15so3749798qtb.2 for ; Thu, 02 Jun 2022 09:31:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=k8kPkxVeNMtdQt55yGN/Nkf+fdNFP4n1eqHNYFzt/EM=; b=RBKGIdGVGyENiynuzvWzxsfKrlShOYG7LDNM6zk7j/0cpFAWM0CNoQ/RikC676Zwip BMHOMh5FSPCGjY61J1z6G+8c1X+4G/XGBmJ3fum6tDtClMi6od+zOdkcyAAKXb0oiOit b12jjL7nGu0mjk8vwPx18er2whDmGOBIM4slv0jp+xyv6iWVZkV8Hkprx2Ft3TnlNr8S F3ZKnuaS0udbsMCk0y55d04otKL6PRXBEyvPN62xIots/ndr10XIEf2q5FJvYZj2hwlD Ppp12ccOTvvIFXm+WxGW6jlLIOBk5xmPC4ktWEJBo/O94h/wW5jv5ZkhHpnGnc8M8pyV u4zw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=k8kPkxVeNMtdQt55yGN/Nkf+fdNFP4n1eqHNYFzt/EM=; b=sSDQoJOZMSzNAnoDsyB+JPqt+KljdhqhibVxxoM3QQwIPiRU2g2lUpV7erQBXCMyTR qMRtdyGCotaVPlEDiui6MqtZBr0NIn0SPcSSnm4SGKHk3Dcp8rCmaX48iO7c6wzbSc3j TE7B4QlDWpPOJJKa/Q/pGl3gojtLukVkVfhesy0kRPdEChUTMWSOymskeopkk+CfuW3e RQlGPxHxfy3iPQqzfU4dmjw6l2Zwcdsy3Gvj9HkP732EkBe0MjMVRTfyJK+MQ4BsBDju lbUetjpp5hqqbXJ58YMHyGRpsACLnYWAKyLiYO2o8HI+b3+iasuCLLTe/xjLAbKC091H vnnA== X-Gm-Message-State: AOAM530JD7iE0ZVtbnGMvH2f1sbiiGF1GMHrLkA9ktnedPoOBmD9hTKE j/U3LhFKVYZ/l/7BF59hWcGeeA== X-Google-Smtp-Source: ABdhPJzLJBnwcPaBtEw6VCmlLIOgqY/pJrxby5kBrBBtbBNr2VGXxQBgSbsEw14Z2kEr0zlwr/+sfg== X-Received: by 2002:ac8:5e49:0:b0:304:c7db:6a2f with SMTP id i9-20020ac85e49000000b00304c7db6a2fmr4316676qtx.274.1654187460731; Thu, 02 Jun 2022 09:31:00 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-142-162-113-129.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.162.113.129]) by smtp.gmail.com with ESMTPSA id ci11-20020a05622a260b00b00304bc2acc25sm3261689qtb.6.2022.06.02.09.30.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Jun 2022 09:30:59 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1nwnit-00GTLv-7Y; Thu, 02 Jun 2022 13:30:59 -0300 Date: Thu, 2 Jun 2022 13:30:59 -0300 From: Jason Gunthorpe To: Logan Gunthorpe Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Stephen Bates , Christoph Hellwig , Dan Williams , Christian =?utf-8?B?S8O2bmln?= , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy , Martin Oliveira , Chaitanya Kulkarni , Ralph Campbell , Bjorn Helgaas Subject: Re: [PATCH v6 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem() Message-ID: <20220602163059.GL2960187@ziepe.ca> References: <20220407154717.7695-1-logang@deltatee.com> <20220407154717.7695-21-logang@deltatee.com> <20220527125501.GD2960187@ziepe.ca> <20220527190307.GG2960187@ziepe.ca> <20220602000038.GK2960187@ziepe.ca> <400baba7-1cd6-09d4-4de9-2a73f08afc79@deltatee.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <400baba7-1cd6-09d4-4de9-2a73f08afc79@deltatee.com> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, Jun 02, 2022 at 10:16:10AM -0600, Logan Gunthorpe wrote: > > Just stuff the pages into the mmap, and your driver unprobe will > > automatically block until all the mmaps are closed - no different than > > having an open file descriptor or something. > > Oh is that what we want? Yes, it is the typical case - eg if you have a sysfs file open unbind hangs indefinitely. Many drivers can't unbind while they have open file descriptors/etc. A couple drivers go out of their way to allow unbinding while a live userspace exists but this can get complicated. Usually there should be a good reason. The module will already be refcounted anyhow because the mmap points to a char file which holds a module reference - meaning a simple rmmod of the driver shouldn't work already.. Jason