From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH 3/5] iommu: Limit iommu_attach/detach_device to devices with their own group Date: Fri, 30 Jan 2015 13:28:14 +0100 Message-ID: <20150130122814.GC3702@8bytes.org> References: <1422317339-22620-1-git-send-email-joro@8bytes.org> <1422317339-22620-4-git-send-email-joro@8bytes.org> <20150128143523.GR1569@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20150128143523.GR1569-5wv7dgnIgG8@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: Will Deacon Cc: "jroedel-l3A5Bk7waGM@public.gmane.org" , Laurent Pinchart , Heiko Stuebner , Arnd Bergmann , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , Thierry Reding , Kukjin Kim , David Woodhouse List-Id: iommu@lists.linux-foundation.org On Wed, Jan 28, 2015 at 02:35:24PM +0000, Will Deacon wrote: > On Tue, Jan 27, 2015 at 12:08:57AM +0000, Joerg Roedel wrote: > > @@ -51,6 +51,7 @@ struct iommu_group { > > void (*iommu_data_release)(void *iommu_data); > > char *name; > > int id; > > + unsigned dev_cnt; > > Is this actually used on a fast path, or can we just inspect the list of > devices on the group instead? Not really a fast path, but we have to hold the group mutex while traversing the list, which could hurt performance somewhere else. Are these 4 bytes a problem? Joerg