On Thu, Aug 22, 2013 at 09:28:23AM -0600, Alex Williamson wrote: >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, >
You mean the .remove_device like intel_iommu_remove_device()? Hmm... this function didn't check the dev->iommu_group and just call iommu_group_remove_device(). I see this guard is put in iommu_bus_notifier(), which will check dev->iommu_group before invoke .remove_device. Let me explain the case to triger the problem a little. On some platform, like powernv, we implement another bus notifier when devices are added or removed in the system. Like Alexey mentioned, he missed the check for dev->iommu_group in the notifier before removing it from iommu_group. This trigger the crash. So do you think it is reasonable to guard the kernel in iommu_group_remove_device(), or we give the platform developers the responsibility to check the dev->iommu_group before calling it? Thanks~ >Alex -- Richard Yang Help you, Help me _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
