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[23.128.96.18]) by mx.google.com with ESMTP id f13si1738734edc.249.2020.10.15.04.05.49; Thu, 15 Oct 2020 04:06:11 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=casper.20170209 header.b=Fycf1Jge; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729644AbgJOGzi (ORCPT + 99 others); Thu, 15 Oct 2020 02:55:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43278 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725208AbgJOGzh (ORCPT ); Thu, 15 Oct 2020 02:55:37 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D338C061755; Wed, 14 Oct 2020 23:55:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=1vZhw/JrbB2T8GVpb8VuLYmLoPDb9JW5DiEoY3ZRNZg=; b=Fycf1JgekT0YbewfwlGQNRxEiq pJjRTzJhLS2LSjjnsUqAEHFvAs/UjhL1lG9jsBd3BRTuTCNFToaNXo2Jz84l6buTUGtzQU8nrm/eS CzQz4jTRPnPfl6blS+u/Oj+MCPFeCSsHgXEXjatO5/9CZiNqsLLyVUT9J8ASYh/VhLRkC5XOs/XhU VZVovGpVYzsa6HeIWVSq3wwywNKJXx4TCv86aLhltul6lPWtqHfE3yGQGewNXjPK9o4VGbk6tZaVk qnOgou5uPSrnmd8aow5y9SZoBcJEqRePqY2hkKbPUtKsr1abESVw4BjKI+PENYB37As7agZTH6gkH /Tfpr9xg==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSxAi-0004Aa-6Z; Thu, 15 Oct 2020 06:55:32 +0000 Date: Thu, 15 Oct 2020 07:55:32 +0100 From: Christoph Hellwig To: Robin Murphy Cc: Christoph Hellwig , Jonathan Marek , David Airlie , freedreno@lists.freedesktop.org, open list , "open list:DRM DRIVER FOR MSM ADRENO GPU" , iommu@lists.linux-foundation.org, Daniel Vetter , "open list:DRM DRIVER FOR MSM ADRENO GPU" , Sean Paul Subject: Re: [PATCH 2/3] drm/msm: add DRM_MSM_GEM_SYNC_CACHE for non-coherent cache maintenance Message-ID: <20201015065532.GA15371@infradead.org> References: <20201001002709.21361-1-jonathan@marek.ca> <20201001002709.21361-3-jonathan@marek.ca> <20201002075321.GA7547@infradead.org> <20201005082914.GA31702@infradead.org> <3e0b91be-e4a4-4ea5-7d58-6e71b8d51932@marek.ca> <20201006072306.GA12834@infradead.org> <148a1660-f0fc-7163-2240-6b94725342b5@marek.ca> <20201007062519.GA23519@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 13, 2020 at 02:42:38PM +0100, Robin Murphy wrote: > I still think this situation would be best handled with a variant of > dma_ops_bypass that also guarantees to bypass SWIOTLB, and can be set > automatically when attaching to an unmanaged IOMMU domain. dma_ops_bypass should mostly do the right thing as-is. swiotlb bouncing is triggered of two things: 1) the dma_mask. This is under control of the driver, and obviously if it is too small for a legit reason we can't just proceed 2) force_dma_unencrypted() - we'd need to do an opt-out here, either by a flag or by being smart and looking for an attached iommu on the device > That way the > device driver can make DMA API calls in the appropriate places that do the > right thing either way, and only needs logic to decide whether to use the > returned DMA addresses directly or ignore them if it knows they're > overridden by its own IOMMU mapping. I'd be happy to review patches for this.