From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by ozlabs.org (Postfix) with ESMTP id 6E6C12C0084 for ; Fri, 23 Aug 2013 01:28:33 +1000 (EST) Message-ID: <1377185303.25163.13.camel@ul30vt.home> Subject: Re: [PATCH 2/2] powerpc/iommu: check dev->iommu_group before remove a device from iommu_group From: Alex Williamson To: Wei Yang Date: Thu, 22 Aug 2013 09:28:23 -0600 In-Reply-To: <20130822075237.GA14479@weiyang.vnet.ibm.com> References: <1376647687-20550-1-git-send-email-weiyang@linux.vnet.ibm.com> <1376647687-20550-3-git-send-email-weiyang@linux.vnet.ibm.com> <520DFBC8.4040509@ozlabs.ru> <20130819012945.GA8342@weiyang.vnet.ibm.com> <52117765.7010205@ozlabs.ru> <20130819015538.GB8342@weiyang.vnet.ibm.com> <5215BC76.10105@ozlabs.ru> <20130822075237.GA14479@weiyang.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: Alexey Kardashevskiy , paulus@au1.ibm.com, benh@au1.ibm.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2013-08-22 at 15:52 +0800, Wei Yang wrote: > On Thu, Aug 22, 2013 at 05:23:34PM +1000, Alexey Kardashevskiy wrote: > >On 08/19/2013 11:55 AM, Wei Yang wrote: > >> On Mon, Aug 19, 2013 at 11:39:49AM +1000, Alexey Kardashevskiy wrote: > >>> On 08/19/2013 11:29 AM, Wei Yang wrote: > >>>> On Fri, Aug 16, 2013 at 08:15:36PM +1000, Alexey Kardashevskiy wrote: > >>>>> On 08/16/2013 08:08 PM, Wei Yang wrote: > >>>>>> --- > >>>>>> arch/powerpc/kernel/iommu.c | 3 ++- > >>>>>> 1 files changed, 2 insertions(+), 1 deletions(-) > >>>>>> > >>>>>> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c > >>>>>> index b20ff17..5abf7c3 100644 > >>>>>> --- a/arch/powerpc/kernel/iommu.c > >>>>>> +++ b/arch/powerpc/kernel/iommu.c > >>>>>> @@ -1149,7 +1149,8 @@ static int iommu_bus_notifier(struct notifier_block *nb, > >>>>>> case BUS_NOTIFY_ADD_DEVICE: > >>>>>> return iommu_add_device(dev); > >>>>>> case BUS_NOTIFY_DEL_DEVICE: > >>>>>> - iommu_del_device(dev); > >>>>>> + if (dev->iommu_group) > >>>>>> + iommu_del_device(dev); > >>>>>> return 0; > >>>>>> default: > >>>>>> return 0; > >>>>>> > >>>>> > >>>>> This one seems redundant, no? > >>>> > >>>> Sorry for the late. > >>>> > >>>> Yes, these two patches have the same purpose to guard the system, while in two > >>>> different places. One is in powernv platform, the other is in the generic iommu > >>>> driver. > >>>> > >>>> The one in powernv platform is used to correct the original logic. > >>>> > >>>> The one in generic iommu driver is to keep system safe in case other platform to > >>>> call iommu_group_remove_device() without the check. > >>> > >>> > >>> But I am moving bus notifier to powernv code (posted a patch last week, > >>> otherwise Freescale's IOMMU conflicted) so this won't be the case. > >> > >> Yes, I see the patch. > >> > >> This means other platforms, besides powernv, will check the dev->iommu_group > >> before remove the device? This would be a convention? > >> > >> If this is the case, the second patch is enough. We don't need to check it in > >> generic iommu driver. > >> > >> Since I am not very familiar with the code convention, I post these two > >> patches together. This doesn't mean I need to push both of them. Your comments > >> are welcome, lets me understand which one is more suitable in this case. > > > > > >Ok. So. I included the check in the bus notifier which I moved to powernv > >platform, I guess I'll repost the series soon. > > Thanks, this check will guard the powernv platform. > > > > >Good luck with pushing the fix for drivers/iommu/iommu.c :) > > > > Alex, > > Sorry for not including you in the very beginning, which may spend you more > efforts to track previous mails in this thread. > > Do you think it is reasonable to check the dev->iommu_group in > iommu_group_remove_device()? Or we can count on the bus notifier to check it? > > Welcome your suggestions~ I don't really see the point of patch 1/2. iommu_group_remove_device() is specifically to remove a device from an iommu_group, so why would you call it on a device that's not part of an iommu_group. If you want to avoid testing dev->iommu_group, then implement the .remove_device callback rather than using the notifier. Thanks, Alex