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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDDCEC433EF for ; Fri, 1 Oct 2021 17:31:56 +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 A8C4061166 for ; Fri, 1 Oct 2021 17:31:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A8C4061166 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=collabora.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id F05566EE63; Fri, 1 Oct 2021 17:31:55 +0000 (UTC) Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [46.235.227.227]) by gabe.freedesktop.org (Postfix) with ESMTPS id 99C5D6EE6E for ; Fri, 1 Oct 2021 17:31:54 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: alyssa) with ESMTPSA id EA7451F452CD Date: Fri, 1 Oct 2021 13:31:48 -0400 From: Alyssa Rosenzweig To: Boris Brezillon Cc: Joerg Roedel , iommu@lists.linux-foundation.org, Rob Herring , Tomeu Vizoso , Alyssa Rosenzweig , Steven Price , Robin Murphy , Will Deacon , linux-arm-kernel@lists.infradead.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH v2 1/5] [RFC]iommu: Add a IOMMU_DEVONLY protection flag Message-ID: References: <20211001143427.1564786-1-boris.brezillon@collabora.com> <20211001143427.1564786-2-boris.brezillon@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211001143427.1564786-2-boris.brezillon@collabora.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" > The IOMMU_DEVONLY flag allows the caller to flag a mappings backed by > device-private buffers. That means other devices or CPUs are not > expected to access the physical memory region pointed by the mapping, > and the MMU driver can safely restrict the shareability domain to the > device itself. > > Will be used by the ARM MMU driver to flag Mali mappings accessed only > by the GPU as Inner-shareable. > > Signed-off-by: Boris Brezillon > --- > include/linux/iommu.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > index d2f3435e7d17..db14781b522f 100644 > --- a/include/linux/iommu.h > +++ b/include/linux/iommu.h > @@ -31,6 +31,13 @@ > * if the IOMMU page table format is equivalent. > */ > #define IOMMU_PRIV (1 << 5) > +/* > + * Mapping is only accessed by the device behind the iommu. That means other > + * devices or CPUs are not expected to access this physical memory region, > + * and the MMU driver can safely restrict the shareability domain to the > + * device itself. > + */ > +#define IOMMU_DEVONLY (1 << 6) > > struct iommu_ops; > struct iommu_group; This seems totally reasonable to me, but it is well-known that I'm not on good terms with the iommu subsystem. Let's wait for Robin to NAK :-P