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Subject: Re: [PATCH 3/4] iommu/of: Don't call iommu_ops->add_device directly
To:     Joerg Roedel <joro@8bytes.org>
Cc:     iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        jroedel@suse.de, Sudeep Holla <sudeep.holla@arm.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Krzysztof Kozlowski <krzk@kernel.org>
From:   Marek Szyprowski <m.szyprowski@samsung.com>
Message-ID: <442867b9-2d36-4b14-56ee-b4bb8e6be4c0@samsung.com>
Date:   Wed, 19 Dec 2018 15:53:51 +0100
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Hi Joerg,

On 2018-12-19 15:34, Joerg Roedel wrote:
> Hi Marek,
>
> thanks for the report!
>
> On Wed, Dec 19, 2018 at 10:54:18AM +0100, Marek Szyprowski wrote:
>> On 2018-12-11 16:05, Joerg Roedel wrote:
>>> From: Joerg Roedel <jroedel@suse.de>
>>>
>>> Make sure to invoke this call-back through the proper
>>> function of the IOMMU-API.
>>>
>>> Signed-off-by: Joerg Roedel <jroedel@suse.de>
>>> ---
>>>  drivers/iommu/of_iommu.c | 6 +++---
>>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
>>> index c5dd63072529..4d4847de727e 100644
>>> --- a/drivers/iommu/of_iommu.c
>>> +++ b/drivers/iommu/of_iommu.c
>>> @@ -218,10 +218,10 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
>>>  		ops = dev->iommu_fwspec->ops;
>>>  	/*
>>>  	 * If we have reason to believe the IOMMU driver missed the initial
>>> -	 * add_device callback for dev, replay it to get things in order.
>>> +	 * probe for dev, replay it to get things in order.
>>>  	 */
>>> -	if (ops && ops->add_device && dev->bus && !dev->iommu_group)
>>> -		err = ops->add_device(dev);
>>> +	if (dev->bus && !dev->iommu_group)
>>> +		err = iommu_probe_device(dev);
>> This change removes a check for NULL ops, what causes NULL pointer
>> exception on first device without IOMMU.
> Bummer, this check was supposed to be in iommu_probe_device(), but
> apparently it got lost. Does the attached patch fix it?

Yes, it fixes this issue.

>> I'm also not sure if this is a good idea to call iommu_probe_device(),
>> which comes from dev->bus->iommu_ops, which might be different from ops
>> from local variable.
> The local variable comes from dev->iommu_fwspec->ops, which should be
> exactly the same as dev->bus->iommu_ops. I'll leave that for now until
> it turns out to be a problem (which I don't expect).
>
>
> Regards,
>
> 	Joerg
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index a2131751dcff..3ed4db334341 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -114,10 +114,14 @@ void iommu_device_unregister(struct iommu_device *iommu)
>  int iommu_probe_device(struct device *dev)
>  {
>  	const struct iommu_ops *ops = dev->bus->iommu_ops;
> +	int ret = -EINVAL;
>  
>  	WARN_ON(dev->iommu_group);
>  
> -	return ops->add_device(dev);
> +	if (ops)
> +		ret = ops->add_device(dev);
> +
> +	return ret;
>  }
>  
>  void iommu_release_device(struct device *dev)
>
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland