linux-kernel - Re: [PATCH v4 2/5] iommu/dma: add support for non-strict mode

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Date:   Thu, 9 Aug 2018 11:46:33 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Zhen Lei <thunder.leizhen@...wei.com>,
        Will Deacon <will.deacon@....com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Cc:     LinuxArm <linuxarm@...wei.com>, Hanjun Guo <guohanjun@...wei.com>,
        Libin <huawei.libin@...wei.com>
Subject: Re: [PATCH v4 2/5] iommu/dma: add support for non-strict mode

On 06/08/18 13:27, Zhen Lei wrote:
> 1. Save the related domain pointer in struct iommu_dma_cookie, make iovad
>     capable call domain->ops->flush_iotlb_all to flush TLB.
> 2. During the iommu domain initialization phase, base on domain->non_strict
>     field to check whether non-strict mode is supported or not. If so, call
>     init_iova_flush_queue to register iovad->flush_cb callback.
> 3. All unmap(contains iova-free) APIs will finally invoke __iommu_dma_unmap
>     -->iommu_dma_free_iova. If the domain is non-strict, call queue_iova to
>     put off iova freeing.
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>   drivers/iommu/dma-iommu.c | 23 +++++++++++++++++++++++
>   drivers/iommu/iommu.c     |  1 +
>   include/linux/iommu.h     |  1 +
>   3 files changed, 25 insertions(+)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index ddcbbdb..213e62a 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -55,6 +55,7 @@ struct iommu_dma_cookie {
>   	};
>   	struct list_head		msi_page_list;
>   	spinlock_t			msi_lock;
> +	struct iommu_domain		*domain;
>   };
> 
>   static inline size_t cookie_msi_granule(struct iommu_dma_cookie *cookie)
> @@ -257,6 +258,17 @@ static int iova_reserve_iommu_regions(struct device *dev,
>   	return ret;
>   }
> 
> +static void iommu_dma_flush_iotlb_all(struct iova_domain *iovad)
> +{
> +	struct iommu_dma_cookie *cookie;
> +	struct iommu_domain *domain;
> +
> +	cookie = container_of(iovad, struct iommu_dma_cookie, iovad);
> +	domain = cookie->domain;
> +
> +	domain->ops->flush_iotlb_all(domain);
> +}
> +
>   /**
>    * iommu_dma_init_domain - Initialise a DMA mapping domain
>    * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie()
> @@ -308,6 +320,14 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>   	}
> 
>   	init_iova_domain(iovad, 1UL << order, base_pfn);
> +
> +	if (domain->non_strict) {
> +		BUG_ON(!domain->ops->flush_iotlb_all);
> +
> +		cookie->domain = domain;

cookie->domain will only be non-NULL if domain->non_strict is true...

> +		init_iova_flush_queue(iovad, iommu_dma_flush_iotlb_all, NULL);
> +	}
> +
>   	if (!dev)
>   		return 0;
> 
> @@ -390,6 +410,9 @@ static void iommu_dma_free_iova(struct iommu_dma_cookie *cookie,
>   	/* The MSI case is only ever cleaning up its most recent allocation */
>   	if (cookie->type == IOMMU_DMA_MSI_COOKIE)
>   		cookie->msi_iova -= size;
> +	else if (cookie->domain && cookie->domain->non_strict)

...so we don't need to re-check non_strict every time here.

> +		queue_iova(iovad, iova_pfn(iovad, iova),
> +				size >> iova_shift(iovad), 0);
>   	else
>   		free_iova_fast(iovad, iova_pfn(iovad, iova),
>   				size >> iova_shift(iovad));
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 63b3756..7811fde 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1263,6 +1263,7 @@ static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
> 
>   	domain->ops  = bus->iommu_ops;
>   	domain->type = type;
> +	domain->non_strict = 0;
>   	/* Assume all sizes by default; the driver may override this later */
>   	domain->pgsize_bitmap  = bus->iommu_ops->pgsize_bitmap;
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 19938ee..0a0fb48 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -88,6 +88,7 @@ struct iommu_domain_geometry {
> 
>   struct iommu_domain {
>   	unsigned type;
> +	int non_strict;

bool?

Robin.

>   	const struct iommu_ops *ops;
>   	unsigned long pgsize_bitmap;	/* Bitmap of page sizes in use */
>   	iommu_fault_handler_t handler;
> --
> 1.8.3
> 
>