linux-kernel - Re: [PATCH v2 1/6] iommu: Move iotlb_sync_map out from __iommu

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Date:   Wed, 25 Nov 2020 16:37:48 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Yong Wu <yong.wu@...iatek.com>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Tomasz Figa <tfiga@...gle.com>,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, youlin.pei@...iatek.com,
        Nicolas Boichat <drinkcat@...omium.org>, anan.sun@...iatek.com,
        chao.hao@...iatek.com, jun.wen@...iatek.com
Subject: Re: [PATCH v2 1/6] iommu: Move iotlb_sync_map out from __iommu_map

On 2020-11-19 06:18, Yong Wu wrote:
> In the end of __iommu_map, It alway call iotlb_sync_map.
> This patch moves iotlb_sync_map out from __iommu_map since it is
> unnecessary to call this for each sg segment especially iotlb_sync_map
> is flush tlb all currently.

I don't see a way to avoid the boilerplate that wouldn't end up making 
things even more ugly and complicated, so:

Reviewed-by: Robin Murphy <robin.murphy@....com>

> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> ---
>   drivers/iommu/iommu.c | 24 +++++++++++++++++++-----
>   1 file changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 8c470f451a32..decef851fa3a 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2407,9 +2407,6 @@ static int __iommu_map(struct iommu_domain *domain, unsigned long iova,
>   		size -= pgsize;
>   	}
>   
> -	if (ops->iotlb_sync_map)
> -		ops->iotlb_sync_map(domain);
> -
>   	/* unroll mapping in case something went wrong */
>   	if (ret)
>   		iommu_unmap(domain, orig_iova, orig_size - size);
> @@ -2422,15 +2419,29 @@ static int __iommu_map(struct iommu_domain *domain, unsigned long iova,
>   int iommu_map(struct iommu_domain *domain, unsigned long iova,
>   	      phys_addr_t paddr, size_t size, int prot)
>   {
> +	const struct iommu_ops *ops = domain->ops;
> +	int ret;
> +
>   	might_sleep();
> -	return __iommu_map(domain, iova, paddr, size, prot, GFP_KERNEL);
> +	ret = __iommu_map(domain, iova, paddr, size, prot, GFP_KERNEL);
> +	if (ret == 0 && ops->iotlb_sync_map)
> +		ops->iotlb_sync_map(domain);
> +
> +	return ret;
>   }
>   EXPORT_SYMBOL_GPL(iommu_map);
>   
>   int iommu_map_atomic(struct iommu_domain *domain, unsigned long iova,
>   	      phys_addr_t paddr, size_t size, int prot)
>   {
> -	return __iommu_map(domain, iova, paddr, size, prot, GFP_ATOMIC);
> +	const struct iommu_ops *ops = domain->ops;
> +	int ret;
> +
> +	ret = __iommu_map(domain, iova, paddr, size, prot, GFP_ATOMIC);
> +	if (ret == 0 && ops->iotlb_sync_map)
> +		ops->iotlb_sync_map(domain);
> +
> +	return ret;
>   }
>   EXPORT_SYMBOL_GPL(iommu_map_atomic);
>   
> @@ -2514,6 +2525,7 @@ static size_t __iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
>   			     struct scatterlist *sg, unsigned int nents, int prot,
>   			     gfp_t gfp)
>   {
> +	const struct iommu_ops *ops = domain->ops;
>   	size_t len = 0, mapped = 0;
>   	phys_addr_t start;
>   	unsigned int i = 0;
> @@ -2544,6 +2556,8 @@ static size_t __iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
>   			sg = sg_next(sg);
>   	}
>   
> +	if (ops->iotlb_sync_map)
> +		ops->iotlb_sync_map(domain);
>   	return mapped;
>   
>   out_err:
>