linux-kernel - RE: [PATCH] iommu: Check dev->iommu in iommu_dev

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Date:   Tue, 26 Jan 2021 16:40:45 +0000
From:   Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
To:     Robin Murphy <robin.murphy@....com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "will@...nel.org" <will@...nel.org>,
        "linuxarm@...neuler.org" <linuxarm@...neuler.org>,
        "Zengtao (B)" <prime.zeng@...ilicon.com>
Subject: RE: [PATCH] iommu: Check dev->iommu in iommu_dev_xxx functions

Hi Robin,

> -----Original Message-----
> From: Robin Murphy [mailto:robin.murphy@....com]
> Sent: 26 January 2021 13:51
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
> Cc: linux-kernel@...r.kernel.org; iommu@...ts.linux-foundation.org;
> jean-philippe@...aro.org; will@...nel.org; linuxarm@...neuler.org; Zengtao
> (B) <prime.zeng@...ilicon.com>
> Subject: Re: [PATCH] iommu: Check dev->iommu in iommu_dev_xxx functions
> 
> On Tue, 26 Jan 2021 13:06:29 +0000
> Shameer Kolothum <shameerali.kolothum.thodi@...wei.com> wrote:
> 
> > The device iommu probe/attach might have failed leaving dev->iommu to
> > NULL and device drivers may still invoke these functions resulting a
> > crash in iommu vendor driver code. Hence make sure we check that.
> >
> > Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
> > ---
> >  drivers/iommu/iommu.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index
> > ffeebda8d6de..cb68153c5cc0 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -2867,7 +2867,7 @@ bool iommu_dev_has_feature(struct device *dev,
> > enum iommu_dev_features feat) {
> >  	const struct iommu_ops *ops = dev->bus->iommu_ops;
> >
> > -	if (ops && ops->dev_has_feat)
> > +	if (dev->iommu && ops && ops->dev_has_feat)
> >  		return ops->dev_has_feat(dev, feat);
> 
> Might make sense to make these more self-contained, e.g.:
> 
> 	if (dev->iommu && dev->iommu->ops->foo)
> 		dev->iommu->ops->foo()

Right. Does that mean adding ops to "struct dev_iommu" or retrieve ops like
below,

if (dev->iommu && dev->iommu->iommu_dev->ops->foo)
 		dev->iommu->iommu_dev->ops->foo()
 
Sorry, not clear to me.

Thanks,
Shameer