From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 41m7hd3VflzDqkP for ; Thu, 9 Aug 2018 10:01:37 +1000 (AEST) Message-ID: Subject: Re: [PATCH 08/20] powerpc/dma: remove the unused dma_nommu_ops export From: Benjamin Herrenschmidt To: Christoph Hellwig , Paul Mackerras , Michael Ellerman , Tony Luck , Fenghua Yu Cc: linuxppc-dev@lists.ozlabs.org, iommu@lists.linux-foundation.org, linux-ia64@vger.kernel.org, Robin Murphy , Konrad Rzeszutek Wilk Date: Thu, 09 Aug 2018 10:01:16 +1000 In-Reply-To: <20180731121625.GA29793@lst.de> References: <20180730163824.10064-1-hch@lst.de> <20180730163824.10064-9-hch@lst.de> <20180731121625.GA29793@lst.de> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2018-07-31 at 14:16 +0200, Christoph Hellwig wrote: > It turns out cxl actually uses it. So for now skip this patch, > although random code in drivers messing with dma ops will need to > be sorted out sooner or later. CXL devices are "special", they bypass the classic iommu in favor of allowing the device to operate using the main processor page tables using an MMU context (so basically the device can use userspace addresses directly), akin to ATS. I think the code currently uses the nommu ops as a way to do a simple kernel mapping for kernel drivers using CXL (not userspace stuff) though. Ben.