linux-kernel - Re: [PATCH] iommu/core: fix bus notifier breakage

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Date:	Thu, 25 Sep 2014 11:15:44 -0400
From:	Mark Salter <msalter@...hat.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
Subject: Re: [PATCH] iommu/core: fix bus notifier breakage

On Thu, 2014-09-25 at 16:47 +0200, Joerg Roedel wrote:
> On Sun, Sep 21, 2014 at 01:58:24PM -0400, Mark Salter wrote:
> > iommu_bus_init() registers a bus notifier on the given bus by using
> > a statically defined notifier block:
> > 
> >   static struct notifier_block iommu_bus_nb = {
> >           .notifier_call = iommu_bus_notifier,
> >   };
> > 
> > This same notifier block is used for all busses. This causes a
> > problem for notifiers registered after iommu has registered this
> > callback on multiple busses. The problem is that a subsequent
> > notifier being registered on a bus which has this iommu notifier
> > will also get linked in to the notifier list of all other busses
> > which have this iommu notifier.
> > 
> > This patch fixes this by allocating the notifier_block at runtime.
> > Some error checking is also added to catch any allocation failure
> > or notifier registration error.
> > 
> > Signed-off-by: Mark Salter <msalter@...hat.com>
> > ---
> >  drivers/iommu/iommu.c | 26 ++++++++++++++++----------
> >  1 file changed, 16 insertions(+), 10 deletions(-)
> 
> Makes sense, applied. Where have you hit this condition where IOMMUs for
> different buses are registered?

arm_smmu_init()

	/* Oh, for a proper bus abstraction */
	if (!iommu_present(&platform_bus_type))
		bus_set_iommu(&platform_bus_type, &arm_smmu_ops);

#ifdef CONFIG_ARM_AMBA
	if (!iommu_present(&amba_bustype))
		bus_set_iommu(&amba_bustype, &arm_smmu_ops);
#endif

#ifdef CONFIG_PCI
	if (!iommu_present(&pci_bus_type))
		bus_set_iommu(&pci_bus_type, &arm_smmu_ops);
#endif


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