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Message-ID: <2024082941-lagging-escapade-d9d8@gregkh>
Date: Thu, 29 Aug 2024 15:52:24 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Sachin Parekh <sachinparekh@...gle.com>
Cc: rafael@...nel.org, will@...nel.org, robin.murphy@....com,
lokeshvutla@...gle.com, linux-kernel@...r.kernel.org,
iommu@...ts.linux.dev
Subject: Re: [RFC PATCH] driver core: platform: Call iommu_release_device in
dma_cleanup
On Thu, Aug 29, 2024 at 12:05:04PM +0000, Sachin Parekh wrote:
> Installing a kernel module that has an iommu node in its
> device tree increments corresponding iommu kernel module
> reference count during driver_register.
> Removing the same kernel module doesn't decrement the
> iommu reference count resulting in error while
> removing the iommu kernel module
Please wrap kernel changelog text at 72 columns like your editor asked
you to :)
> $ modprobe arm-smmu-v3
> $ modprobe test_module
> $ modprobe -r test_module
> $ modprobe -r arm-smmu-v3
> modprobe: can't unload module arm_smmu_v3: Resource temporarily unavailable
Does this happen for any in-kernel driver?
Why has this not been noticed before?
>
> Cause:
> platform_driver_register
> ...
> -> platform_dma_configure
> ...
> -> iommu_probe_device (Increments reference count)
>
> platform_driver_unregister
> ...
> -> platform_dma_cleanup
> ...
> -> No corresponding iommu_release_device call
>
> Fix:
> Call iommu_release_device in platform_dma_cleanup to remove the
> iommu from the corresponding kernel module
>
> Signed-off-by: Sachin Parekh <sachinparekh@...gle.com>
What commit id does this fix?
> ---
> drivers/base/platform.c | 3 +++
> drivers/iommu/iommu.c | 3 +--
> include/linux/iommu.h | 1 +
> 3 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 4c3ee6521ba5..c8125325a5e9 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -1467,6 +1467,9 @@ static void platform_dma_cleanup(struct device *dev)
>
> if (!drv->driver_managed_dma)
> iommu_device_unuse_default_domain(dev);
> +
> + if (dev_of_node(dev))
> + iommu_release_device(dev);
Are you sure that all devices that pass this should have this call made?
How well was this tested on different systems?
thanks,
greg k-h
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