linux-kernel - Re: [PATCH 1/1] iommu: Remove iommu

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Message-ID: <aceec535-a726-4fcb-9698-3cabe163c15e@intel.com>
Date: Mon, 30 Sep 2024 19:23:05 +0800
From: Yi Liu <yi.l.liu@...el.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>, "Will
 Deacon" <will@...nel.org>, Robin Murphy <robin.murphy@....com>, "Jason
 Gunthorpe" <jgg@...pe.ca>, Kevin Tian <kevin.tian@...el.com>
CC: <iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>, Jason Gunthorpe
	<jgg@...dia.com>
Subject: Re: [PATCH 1/1] iommu: Remove iommu_present()

On 2024/9/30 08:42, Lu Baolu wrote:
> The last callsite of iommu_present() is removed by commit <45c690aea8ee>
> ("drm/tegra: Use iommu_paging_domain_alloc()"). Remove it to avoid dead
> code.
> 
> Fixes: 45c690aea8ee ("drm/tegra: Use iommu_paging_domain_alloc()")
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> ---

just curious, why a fix tag here. It is not a bug. is it?

Reviewed-by: Yi Liu <yi.l.liu@...el.com>

>   include/linux/iommu.h |  6 ------
>   drivers/iommu/iommu.c | 25 -------------------------
>   2 files changed, 31 deletions(-)
> 
> Change log:
> - Originally posted here
>    https://lore.kernel.org/r/20240610085555.88197-21-baolu.lu@linux.intel.com
>    After several patches in that series were merged, this patch is
>    targeted for 6.12-rc.
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index bd722f473635..62d1b85c80d3 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -785,7 +785,6 @@ static inline void iommu_iotlb_gather_init(struct iommu_iotlb_gather *gather)
>   }
>   
>   extern int bus_iommu_probe(const struct bus_type *bus);
> -extern bool iommu_present(const struct bus_type *bus);
>   extern bool device_iommu_capable(struct device *dev, enum iommu_cap cap);
>   extern bool iommu_group_has_isolated_msi(struct iommu_group *group);
>   extern struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus);
> @@ -1081,11 +1080,6 @@ struct iommu_iotlb_gather {};
>   struct iommu_dirty_bitmap {};
>   struct iommu_dirty_ops {};
>   
> -static inline bool iommu_present(const struct bus_type *bus)
> -{
> -	return false;
> -}
> -
>   static inline bool device_iommu_capable(struct device *dev, enum iommu_cap cap)
>   {
>   	return false;
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 83c8e617a2c5..7bfd2caaf33b 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1840,31 +1840,6 @@ int bus_iommu_probe(const struct bus_type *bus)
>   	return 0;
>   }
>   
> -/**
> - * iommu_present() - make platform-specific assumptions about an IOMMU
> - * @bus: bus to check
> - *
> - * Do not use this function. You want device_iommu_mapped() instead.
> - *
> - * Return: true if some IOMMU is present and aware of devices on the given bus;
> - * in general it may not be the only IOMMU, and it may not have anything to do
> - * with whatever device you are ultimately interested in.
> - */
> -bool iommu_present(const struct bus_type *bus)
> -{
> -	bool ret = false;
> -
> -	for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
> -		if (iommu_buses[i] == bus) {
> -			spin_lock(&iommu_device_lock);
> -			ret = !list_empty(&iommu_device_list);
> -			spin_unlock(&iommu_device_lock);
> -		}
> -	}
> -	return ret;
> -}
> -EXPORT_SYMBOL_GPL(iommu_present);
> -
>   /**
>    * device_iommu_capable() - check for a general IOMMU capability
>    * @dev: device to which the capability would be relevant, if available

-- 
Regards,
Yi Liu