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 X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6878BC2BA19 for ; Mon, 13 Apr 2020 13:27:35 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2550720692 for ; Mon, 13 Apr 2020 13:27:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2550720692 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CD0998E0116; Mon, 13 Apr 2020 09:27:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CA5E78E0104; Mon, 13 Apr 2020 09:27:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BBCF38E0116; Mon, 13 Apr 2020 09:27:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0022.hostedemail.com [216.40.44.22]) by kanga.kvack.org (Postfix) with ESMTP id A49848E0104 for ; Mon, 13 Apr 2020 09:27:34 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 6E22D52B3 for ; Mon, 13 Apr 2020 13:27:34 +0000 (UTC) X-FDA: 76702908828.08.neck67_4215ee3d2b323 X-HE-Tag: neck67_4215ee3d2b323 X-Filterd-Recvd-Size: 2417 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf25.hostedemail.com (Postfix) with ESMTP for ; Mon, 13 Apr 2020 13:27:34 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id AEBD868BEB; Mon, 13 Apr 2020 15:27:30 +0200 (CEST) Date: Mon, 13 Apr 2020 15:27:30 +0200 From: Christoph Hellwig To: Yan Zhao Cc: Christoph Hellwig , Linus Torvalds , Andrew Morton , Jens Axboe , Felipe Balbi , amd-gfx@lists.freedesktop.org, "Michael S. Tsirkin" , Felix Kuehling , linux-usb@vger.kernel.org, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Zhenyu Wang , virtualization@lists.linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Al Viro , intel-gfx@lists.freedesktop.org, Alex Deucher , intel-gvt-dev@lists.freedesktop.org, Jason Wang , Zhi Wang Subject: Re: [PATCH 2/6] i915/gvt/kvm: a NULL ->mm does not mean a thread is a kthread Message-ID: <20200413132730.GB14455@lst.de> References: <20200404094101.672954-1-hch@lst.de> <20200404094101.672954-3-hch@lst.de> <20200407030845.GA10586@joy-OptiPlex-7040> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200407030845.GA10586@joy-OptiPlex-7040> User-Agent: Mutt/1.5.17 (2007-11-01) 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 Mon, Apr 06, 2020 at 11:08:46PM -0400, Yan Zhao wrote: > hi > we were removing this code. see > https://lore.kernel.org/kvm/20200313031109.7989-1-yan.y.zhao@intel.com/ This didn't make 5.7-rc1. > The implementation of vfio_dma_rw() has been in vfio next tree. > https://github.com/awilliam/linux-vfio/commit/8d46c0cca5f4dc0538173d62cd36b1119b5105bc This made 5.7-rc1, so I'll update the series to take it into account. T > in vfio_dma_rw(), we still use > bool kthread = current->mm == NULL. > because if current->mm != NULL and current->flags & PF_KTHREAD, instead > of calling use_mm(), we first check if (current->mm == mm) and allow copy_to_user() if it's true. > > Do you think it's all right? I can't think of another way for a kernel thread to have a mm indeed.