From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH 3/5] iommu/arm-smmu: Introduce stream ID masking Date: Tue, 8 Oct 2013 16:10:07 +0100 Message-ID: <20131008151007.GD21189@mudshark.cambridge.arm.com> References: <1381224444-27303-1-git-send-email-andreas.herrmann@calxeda.com> <1381224444-27303-4-git-send-email-andreas.herrmann@calxeda.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1381224444-27303-4-git-send-email-andreas.herrmann-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Andreas Herrmann Cc: "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , Rob Herring , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: iommu@lists.linux-foundation.org On Tue, Oct 08, 2013 at 10:27:22AM +0100, Andreas Herrmann wrote: > Ie. use a mask based on smr_mask_bits to map all stream IDs of an SMMU > to one context. > > This behaviour is controlled per SMMU node with DT property > "arm,smmu-mask-stream-ids" and is only allowed if just a single master > is attached to an SMMU. If the option is specified, all stream-ids > that are provided in DT for the single master have no relevance. > > This is useful/convenient if a master has more than 8 stream-ids or if > not all stream-ids are known for a master device. Hmmm, this really scares me. What's the use-case? I worry about people inadvertently putting devices into an iommu domain because they happen to be included in a mask. Your solution seems to be targetting a single master with lots of IDs -- is this a PCI RC? Will