From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH] iommu/arm-smmu-v3: avoid over allocating for l2 stream tables Date: Tue, 20 Dec 2016 10:22:09 +0000 Message-ID: <20161220102209.GC10132@arm.com> References: <1482179200-4264-1-git-send-email-nwatters@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1482179200-4264-1-git-send-email-nwatters-sgV2jX0FEOL9JmXXK+q4OQ@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: Nate Watterson Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hi Nate, On Mon, Dec 19, 2016 at 03:26:40PM -0500, Nate Watterson wrote: > Currently, all l2 stream tables are being allocated with space for > (1< physically supports. To avoid allocating memory for inaccessible > stes, this patch limits the span of an l2 table to be no larger > than the sid size of the smmu to which it belongs. > > Signed-off-by: Nate Watterson > --- > drivers/iommu/arm-smmu-v3.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) I can't help but think you'd be better off using a linear stream table in this scenario. If we hack the feature check for ARM_SMMU_FEAT_2_LVL_STRTAB so that it doesn't report support for 2 level tables if the number of sids is less than that covered by a single l2 entry, would that solve your problem? Will