Messages in this thread Patch in this message | | | From | Shameerali Kolothum Thodi <> | Subject | RE: [PATCH v2] iommu: Check dev->iommu in iommu_dev_xxx functions | Date | Fri, 12 Feb 2021 17:28:34 +0000 |
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> -----Original Message----- > From: Shameerali Kolothum Thodi > Sent: 12 February 2021 16:45 > To: 'Robin Murphy' <robin.murphy@arm.com>; linux-kernel@vger.kernel.org; > iommu@lists.linux-foundation.org > Cc: joro@8bytes.org; jean-philippe@linaro.org; will@kernel.org; Zengtao (B) > <prime.zeng@hisilicon.com>; linuxarm@openeuler.org > Subject: RE: [PATCH v2] iommu: Check dev->iommu in iommu_dev_xxx functions > > > > > -----Original Message----- > > From: Robin Murphy [mailto:robin.murphy@arm.com] > > Sent: 12 February 2021 16:39 > > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>; > > linux-kernel@vger.kernel.org; iommu@lists.linux-foundation.org > > Cc: joro@8bytes.org; jean-philippe@linaro.org; will@kernel.org; Zengtao (B) > > <prime.zeng@hisilicon.com>; linuxarm@openeuler.org > > Subject: Re: [PATCH v2] iommu: Check dev->iommu in iommu_dev_xxx > functions > > > > On 2021-02-12 14:54, Shameerali Kolothum Thodi wrote: > > > Hi Robin/Joerg, > > > > > >> -----Original Message----- > > >> From: Shameer Kolothum > [mailto:shameerali.kolothum.thodi@huawei.com] > > >> Sent: 01 February 2021 12:41 > > >> To: linux-kernel@vger.kernel.org; iommu@lists.linux-foundation.org > > >> Cc: joro@8bytes.org; robin.murphy@arm.com; jean-philippe@linaro.org; > > >> will@kernel.org; Zengtao (B) <prime.zeng@hisilicon.com>; > > >> linuxarm@openeuler.org > > >> Subject: [Linuxarm] [PATCH v2] iommu: Check dev->iommu in > > iommu_dev_xxx > > >> functions > > >> > > >> The device iommu probe/attach might have failed leaving dev->iommu > > >> to NULL and device drivers may still invoke these functions resulting > > >> in a crash in iommu vendor driver code. Hence make sure we check that. > > >> > > >> Also added iommu_ops to the "struct dev_iommu" and set it if the dev > > >> is successfully associated with an iommu. > > >> > > >> Fixes: a3a195929d40 ("iommu: Add APIs for multiple domains per > device") > > >> Signed-off-by: Shameer Kolothum > > <shameerali.kolothum.thodi@huawei.com> > > >> --- > > >> v1 --> v2: > > >> -Added iommu_ops to struct dev_iommu based on the discussion with > > Robin. > > >> -Rebased against iommu-tree core branch. > > > > > > A gentle ping on this... > > > > Is there a convincing justification for maintaining yet another copy of > > the ops pointer rather than simply dereferencing iommu_dev->ops at point > > of use? > > > > TBH, nothing I can think of now. That was mainly the way I interpreted your > suggestion > from the v1. Now it looks like you didn’t mean it :). I am Ok to rework it to > dereference > it from iommu_dev. Please let me know.
So we can do something like this,
index fd76e2f579fe..5fd31a3cec18 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -2865,10 +2865,12 @@ EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids); */ int iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features feat) { - const struct iommu_ops *ops = dev->bus->iommu_ops; + if (dev->iommu && dev->iommu->iommu_dev && dev->iommu->iommu_dev->ops) + struct iommu_ops *ops = dev->iommu->iommu_dev->ops; - if (ops && ops->dev_enable_feat) - return ops->dev_enable_feat(dev, feat); + if (ops->dev_enable_feat) + return ops->dev_enable_feat(dev, feat); + } return -ENODEV; } Again, not sure we need to do the checking for iommu->dev and ops here. If the dev->iommu is set, is it safe to assume that we have a valid iommu->iommu_dev and ops always? (May be it is safer to do the checking in case something else breaks this assumption in future). Please let me know your thoughts.
Thanks, Shameer
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