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=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 EB9ECC2BA2B for ; Tue, 14 Apr 2020 00:13:55 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C896A20768 for ; Tue, 14 Apr 2020 00:13:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C896A20768 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2C8586E42E; Tue, 14 Apr 2020 00:13:55 +0000 (UTC) Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by gabe.freedesktop.org (Postfix) with ESMTPS id 731DC6E42D; Tue, 14 Apr 2020 00:13:53 +0000 (UTC) IronPort-SDR: LABzmBzP4iD3hXYGMjALoa2ev3cUycAtjg5kfTLlPMFfqp4oqPg8clLqBVuSNB4EoL4id7Wq5U Dri14JugCuIg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Apr 2020 17:13:53 -0700 IronPort-SDR: WwSP/bjwzVqCvzpfDJVQx7mHVD9DqAVfA90u9u6YJ0BE3eg8B7Aus6XqC75wdrzGtPX0vlI9oI I6IjfgU71shQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,380,1580803200"; d="scan'208";a="277078198" Received: from joy-optiplex-7040.sh.intel.com (HELO joy-OptiPlex-7040) ([10.239.13.16]) by fmsmga004.fm.intel.com with ESMTP; 13 Apr 2020 17:13:48 -0700 Date: Mon, 13 Apr 2020 20:04:10 -0400 From: Yan Zhao To: Christoph Hellwig Message-ID: <20200414000410.GE10586@joy-OptiPlex-7040> References: <20200404094101.672954-1-hch@lst.de> <20200404094101.672954-3-hch@lst.de> <20200407030845.GA10586@joy-OptiPlex-7040> <20200413132730.GB14455@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200413132730.GB14455@lst.de> User-Agent: Mutt/1.9.4 (2018-02-28) Subject: Re: [Intel-gfx] [PATCH 2/6] i915/gvt/kvm: a NULL ->mm does not mean a thread is a kthread X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Yan Zhao Cc: Jens Axboe , Felipe Balbi , "Michael S. Tsirkin" , Linus Torvalds , Jason Wang , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, io-uring@vger.kernel.org, linux-mm@kvack.org, intel-gfx@lists.freedesktop.org, linux-fsdevel@vger.kernel.org, Alex Deucher , Andrew Morton , virtualization@lists.linux-foundation.org, intel-gvt-dev@lists.freedesktop.org, Felix Kuehling , Al Viro Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Mon, Apr 13, 2020 at 03:27:30PM +0200, Christoph Hellwig wrote: > 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. for example, before calling to vfio_dma_rw(), a kernel thread has already called use_mm(), then its current->mm is not null, and it has flag PF_KTHREAD. in this case, we just want to allow the copy_to_user() directly if current->mm == mm, rather than call another use_mm() again. do you think it makes sense? Thanks Yan > _______________________________________________ > intel-gvt-dev mailing list > intel-gvt-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx