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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 371EFC433DB for ; Tue, 9 Feb 2021 06:58:44 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (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 8329C64EB6 for ; Tue, 9 Feb 2021 06:58:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8329C64EB6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 3857387267; Tue, 9 Feb 2021 06:58:43 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hty9nPNMfm5v; Tue, 9 Feb 2021 06:58:42 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id 0DF178723B; Tue, 9 Feb 2021 06:58:42 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id E2EB3C0174; Tue, 9 Feb 2021 06:58:41 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id D49F7C013A for ; Tue, 9 Feb 2021 06:58:40 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id BB97587241 for ; Tue, 9 Feb 2021 06:58:40 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id RgMGnPb8Xokz for ; Tue, 9 Feb 2021 06:58:40 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by hemlock.osuosl.org (Postfix) with ESMTPS id 3C1A38723B for ; Tue, 9 Feb 2021 06:58:40 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id DA80D64E9A; Tue, 9 Feb 2021 06:58:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612853919; bh=dpxVE0srNtqxA2P2gotaZ3bV8h2QUfJrlvUUTfe0l7o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TXzbsFhDpAQgj9QwPWKvmB1zj6vFiKg4V4CTlVCZzGXPcxBW49yvO/txzd5T2Ii+w rtL1/wYnZETAmKBFTPqDlkEsOY+vxAe9mVCFLWZ97V8boxpU4loubPLrclacpCX3FY zrcJswcPX2TBjIjas307svqNOUapi81jMEm1i7hk= Date: Tue, 9 Feb 2021 07:58:35 +0100 From: Greg Kroah-Hartman To: Sumit Garg Subject: Re: DMA direct mapping fix for 5.4 and earlier stable branches Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Cc: Daniel Thompson , Linux Kernel Mailing List , stable , obayashi.yoshimasa@socionext.com, iommu@lists.linux-foundation.org, robin.murphy@arm.com, hch@lst.de 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, Feb 09, 2021 at 11:39:25AM +0530, Sumit Garg wrote: > Hi Christoph, Greg, > > Currently we are observing an incorrect address translation > corresponding to DMA direct mapping methods on 5.4 stable kernel while > sharing dmabuf from one device to another where both devices have > their own coherent DMA memory pools. What devices have this problem? And why can't then just use 5.10 to solve this issue as that problem has always been present for them, right? > I am able to root cause this issue which is caused by incorrect virt > to phys translation for addresses belonging to vmalloc space using > virt_to_page(). But while looking at the mainline kernel, this patch > [1] changes address translation from virt->to->phys to dma->to->phys > which fixes the issue observed on 5.4 stable kernel as well (minimal > fix [2]). > > So I would like to seek your suggestion for backport to stable kernels > (5.4 or earlier) as to whether we should backport the complete > mainline commit [1] or we should just apply the minimal fix [2]? Whenever you try to create a "minimal" fix, 90% of the time it is wrong and does not work and I end up having to deal with the mess. What prevents you from doing the real thing here? Are the patches to big? And again, why not just use 5.10 for this hardware? What hardware is it? thanks, greg k-h _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 7060EC433DB for ; Tue, 9 Feb 2021 06:59:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3340E64EB6 for ; Tue, 9 Feb 2021 06:59:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230144AbhBIG7Z (ORCPT ); Tue, 9 Feb 2021 01:59:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:32816 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229464AbhBIG7W (ORCPT ); Tue, 9 Feb 2021 01:59:22 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id DA80D64E9A; Tue, 9 Feb 2021 06:58:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612853919; bh=dpxVE0srNtqxA2P2gotaZ3bV8h2QUfJrlvUUTfe0l7o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TXzbsFhDpAQgj9QwPWKvmB1zj6vFiKg4V4CTlVCZzGXPcxBW49yvO/txzd5T2Ii+w rtL1/wYnZETAmKBFTPqDlkEsOY+vxAe9mVCFLWZ97V8boxpU4loubPLrclacpCX3FY zrcJswcPX2TBjIjas307svqNOUapi81jMEm1i7hk= Date: Tue, 9 Feb 2021 07:58:35 +0100 From: Greg Kroah-Hartman To: Sumit Garg Cc: hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com, iommu@lists.linux-foundation.org, Linux Kernel Mailing List , stable , Daniel Thompson , obayashi.yoshimasa@socionext.com Subject: Re: DMA direct mapping fix for 5.4 and earlier stable branches Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 09, 2021 at 11:39:25AM +0530, Sumit Garg wrote: > Hi Christoph, Greg, > > Currently we are observing an incorrect address translation > corresponding to DMA direct mapping methods on 5.4 stable kernel while > sharing dmabuf from one device to another where both devices have > their own coherent DMA memory pools. What devices have this problem? And why can't then just use 5.10 to solve this issue as that problem has always been present for them, right? > I am able to root cause this issue which is caused by incorrect virt > to phys translation for addresses belonging to vmalloc space using > virt_to_page(). But while looking at the mainline kernel, this patch > [1] changes address translation from virt->to->phys to dma->to->phys > which fixes the issue observed on 5.4 stable kernel as well (minimal > fix [2]). > > So I would like to seek your suggestion for backport to stable kernels > (5.4 or earlier) as to whether we should backport the complete > mainline commit [1] or we should just apply the minimal fix [2]? Whenever you try to create a "minimal" fix, 90% of the time it is wrong and does not work and I end up having to deal with the mess. What prevents you from doing the real thing here? Are the patches to big? And again, why not just use 5.10 for this hardware? What hardware is it? thanks, greg k-h