From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933878Ab3CUQfc (ORCPT ); Thu, 21 Mar 2013 12:35:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:9861 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755484Ab3CUQfb (ORCPT ); Thu, 21 Mar 2013 12:35:31 -0400 Message-ID: <1363883719.2747.13.camel@ul30vt.home> Subject: Re: [PATCH] iommu: add a function to find an iommu group by id From: Alex Williamson To: Alexey Kardashevskiy Cc: Joerg Roedel , Benjamin Herrenschmidt , David Gibson , Paul Mackerras , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org Date: Thu, 21 Mar 2013 10:35:19 -0600 In-Reply-To: <1363852122-17974-1-git-send-email-aik@ozlabs.ru> References: <1363852122-17974-1-git-send-email-aik@ozlabs.ru> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2013-03-21 at 18:48 +1100, Alexey Kardashevskiy wrote: > As IOMMU groups are exposed to the user space by their numbers, > the user space can use them in various kernel APIs so the kernel > might need an API to find a group by its ID. > > As an example, QEMU VFIO on PPC64 platform needs it to associate > a logical bus number (LIOBN) with a specific IOMMU group in order > to support in-kernel handling of DMA map/unmap requests. > > The patch adds the iommu_group_find(id) function which performs > such search. > > Signed-off-by: Alexey Kardashevskiy > --- > drivers/iommu/iommu.c | 26 ++++++++++++++++++++++++++ > include/linux/iommu.h | 1 + > 2 files changed, 27 insertions(+) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index b0afd3d..6340cac 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -205,6 +205,32 @@ printk("%s %u grp %d\n", __func__, __LINE__, iommu_group_id(group)); > } > EXPORT_SYMBOL_GPL(iommu_group_alloc); > > +struct iommu_group *iommu_group_find(int id) > +{ > + struct kobject *group_kobj; > + struct iommu_group *grp; > + const char *name; > + > + if (!iommu_group_kset) > + return NULL; > + > + name = kasprintf(GFP_KERNEL, "%d", id); > + if (!name) > + return NULL; > + > + group_kobj = kset_find_obj(iommu_group_kset, name); > + kfree(name); > + > + if (!group_kobj) > + return NULL; > + > + grp = container_of(group_kobj, struct iommu_group, kobj); > + BUG_ON(grp->id != id); > + > + return grp; > +} > +EXPORT_SYMBOL_GPL(iommu_group_find); Don't you need to do some reference counting here? Otherwise there's no guarantee the returned pointer is still valid by the time it's used. The interface should probably be iommu_group_get_by_id(). Thanks, Alex > + > /** > * iommu_group_get_iommudata - retrieve iommu_data registered for a group > * @group: the group > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > index f3b99e1..20281d5 100644 > --- a/include/linux/iommu.h > +++ b/include/linux/iommu.h > @@ -113,6 +113,7 @@ struct iommu_ops { > extern int bus_set_iommu(struct bus_type *bus, struct iommu_ops *ops); > extern bool iommu_present(struct bus_type *bus); > extern struct iommu_domain *iommu_domain_alloc(struct bus_type *bus); > +extern struct iommu_group *iommu_group_find(int id); > extern void iommu_domain_free(struct iommu_domain *domain); > extern int iommu_attach_device(struct iommu_domain *domain, > struct device *dev);