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Date:   Fri, 30 Jul 2021 11:23:32 +0200
From:   Jean-Philippe Brucker <jean-philippe@linaro.org>
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     joro@8bytes.org, will@kernel.org, linux-kernel@vger.kernel.org,
        dianders@chromium.org, iommu@lists.linux-foundation.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 14/24] iommu: Introduce explicit type for non-strict
 DMA domains
Message-ID: <YQPFFCnYDtmQkdvM@myrica>
References: <cover.1627468308.git.robin.murphy@arm.com>
 <59a4d350c32a83e21de5dcfe6f041f38b0c35b82.1627468309.git.robin.murphy@arm.com>
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On Wed, Jul 28, 2021 at 04:58:35PM +0100, Robin Murphy wrote:
> Promote the difference between strict and non-strict DMA domains from an
> internal detail to a distinct domain feature and type, to pave the road
> for exposing it through the sysfs default domain interface.
> 
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

> ---
>  drivers/iommu/dma-iommu.c |  2 +-
>  drivers/iommu/iommu.c     |  8 ++++++--
>  include/linux/iommu.h     | 11 +++++++++++
>  3 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index e28396cea6eb..8b3545c01077 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1311,7 +1311,7 @@ void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 dma_limit)
>  	 * The IOMMU core code allocates the default DMA domain, which the
>  	 * underlying IOMMU driver needs to support via the dma-iommu layer.
>  	 */
> -	if (domain->type == IOMMU_DOMAIN_DMA) {
> +	if (iommu_is_dma_domain(domain)) {
>  		if (iommu_dma_init_domain(domain, dma_base, dma_limit, dev))
>  			goto out_err;
>  		dev->dma_ops = &iommu_dma_ops;
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index fa8109369f74..982545234cf3 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -115,6 +115,7 @@ static const char *iommu_domain_type_str(unsigned int t)
>  	case IOMMU_DOMAIN_UNMANAGED:
>  		return "Unmanaged";
>  	case IOMMU_DOMAIN_DMA:
> +	case IOMMU_DOMAIN_DMA_FQ:
>  		return "Translated";
>  	default:
>  		return "Unknown";
> @@ -552,6 +553,9 @@ static ssize_t iommu_group_show_type(struct iommu_group *group,
>  		case IOMMU_DOMAIN_DMA:
>  			type = "DMA\n";
>  			break;
> +		case IOMMU_DOMAIN_DMA_FQ:
> +			type = "DMA-FQ\n";
> +			break;
>  		}
>  	}
>  	mutex_unlock(&group->mutex);
> @@ -765,7 +769,7 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
>  	unsigned long pg_size;
>  	int ret = 0;
>  
> -	if (!domain || domain->type != IOMMU_DOMAIN_DMA)
> +	if (!domain || !iommu_is_dma_domain(domain))
>  		return 0;
>  
>  	BUG_ON(!domain->pgsize_bitmap);
> @@ -1947,7 +1951,7 @@ static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
>  	/* Assume all sizes by default; the driver may override this later */
>  	domain->pgsize_bitmap  = bus->iommu_ops->pgsize_bitmap;
>  
> -	if (type == IOMMU_DOMAIN_DMA && iommu_get_dma_cookie(domain)) {
> +	if (iommu_is_dma_domain(domain) && iommu_get_dma_cookie(domain)) {
>  		iommu_domain_free(domain);
>  		domain = NULL;
>  	}
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 141779d76035..046ba4d54cd2 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -61,6 +61,7 @@ struct iommu_domain_geometry {
>  #define __IOMMU_DOMAIN_DMA_API	(1U << 1)  /* Domain for use in DMA-API
>  					      implementation              */
>  #define __IOMMU_DOMAIN_PT	(1U << 2)  /* Domain is identity mapped   */
> +#define __IOMMU_DOMAIN_DMA_FQ	(1U << 3)  /* DMA-API uses flush queue    */
>  
>  /*
>   * This are the possible domain-types
> @@ -73,12 +74,17 @@ struct iommu_domain_geometry {
>   *	IOMMU_DOMAIN_DMA	- Internally used for DMA-API implementations.
>   *				  This flag allows IOMMU drivers to implement
>   *				  certain optimizations for these domains
> + *	IOMMU_DOMAIN_DMA_FQ	- As above, but definitely using batched TLB
> + *				  invalidation.
>   */
>  #define IOMMU_DOMAIN_BLOCKED	(0U)
>  #define IOMMU_DOMAIN_IDENTITY	(__IOMMU_DOMAIN_PT)
>  #define IOMMU_DOMAIN_UNMANAGED	(__IOMMU_DOMAIN_PAGING)
>  #define IOMMU_DOMAIN_DMA	(__IOMMU_DOMAIN_PAGING |	\
>  				 __IOMMU_DOMAIN_DMA_API)
> +#define IOMMU_DOMAIN_DMA_FQ	(__IOMMU_DOMAIN_PAGING |	\
> +				 __IOMMU_DOMAIN_DMA_API |	\
> +				 __IOMMU_DOMAIN_DMA_FQ)
>  
>  struct iommu_domain {
>  	unsigned type;
> @@ -90,6 +96,11 @@ struct iommu_domain {
>  	struct iommu_dma_cookie *iova_cookie;
>  };
>  
> +static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
> +{
> +	return domain->type & __IOMMU_DOMAIN_DMA_API;
> +}
> +
>  enum iommu_cap {
>  	IOMMU_CAP_CACHE_COHERENCY,	/* IOMMU can enforce cache coherent DMA
>  					   transactions */
> -- 
> 2.25.1
> 
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