linux-kernel - Re: [PATCH 3/4] iommu/of: Don't call iommu_ops->add

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Date:   Wed, 19 Dec 2018 10:54:18 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Joerg Roedel <joro@...tes.org>, iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org, jroedel@...e.de,
        Sudeep Holla <sudeep.holla@....com>,
        Robin Murphy <robin.murphy@....com>,
        Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [PATCH 3/4] iommu/of: Don't call iommu_ops->add_device directly

Hi Joerg,

This patch landed in today's linux-next and causes a regression.

On 2018-12-11 16:05, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
>
> Make sure to invoke this call-back through the proper
> function of the IOMMU-API.
>
> Signed-off-by: Joerg Roedel <jroedel@...e.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.

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.

>  
>  	/* Ignore all other errors apart from EPROBE_DEFER */
>  	if (err == -EPROBE_DEFER) {

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland