Re: [PATCH V5 3/5] iommu/dma-iommu: Handle deferred devices

From: Hillf Danton <hdanton@sina•com>
To: Tom Murphy <murphyt7@tcd•ie>
Cc: Heiko Stuebner <heiko@sntech•de>,
	virtualization@lists•linux-foundation.org,
	linux-tegra@vger•kernel.org,
	Thierry Reding <thierry.reding@gmail•com>,
	Will Deacon <will@kernel•org>,
	Marek Szyprowski <m.szyprowski@samsung•com>,
	Jean-Philippe Brucker <jean-philippe@linaro•org>,
	linux-samsung-soc@vger•kernel.org, Joerg Roedel <joro@8bytes•org>,
	iommu@lists•linux-foundation.org,
	Krzysztof Kozlowski <krzk@kernel•org>,
	Jonathan Hunter <jonathanh@nvidia•com>,
	linux-rockchip@lists•infradead.org,
	Andy Gross <agross@kernel•org>,
	Gerald Schaefer <gerald.schaefer@de•ibm.com>,
	linux-s390@vger•kernel.org, linux-arm-msm@vger•kernel.org,
	linux-mediatek@lists•infradead.org,
	Matthias Brugger <matthias.bgg@gmail•com>,
	linux-arm-kernel@lists•infradead.org,
	David Woodhouse <dwmw2@infradead•org>,
	linux-kernel@vger•kernel.org, Rob Clark <robdclark@gmail•com>,
	Kukjin Kim <kgene@kernel•org>,
	Robin Murphy <robin.murphy@arm•com>
Subject: Re: [PATCH V5 3/5] iommu/dma-iommu: Handle deferred devices
Date: Sat, 17 Aug 2019 11:39:14 +0800	[thread overview]
Message-ID: <20190817033914.4812-1-hdanton@sina.com> (raw)
In-Reply-To: <20190815110944.3579-1-murphyt7@tcd.ie>

On Thu, 15 Aug 2019 12:09:41 +0100 Tom Murphy wrote:
> 
> Handle devices which defer their attach to the iommu in the dma-iommu api
> 
> Signed-off-by: Tom Murphy <murphyt7@tcd•ie>
> ---
>  drivers/iommu/dma-iommu.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 2712fbc68b28..906b7fa14d3c 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -22,6 +22,7 @@
>  #include <linux/pci.h>
>  #include <linux/scatterlist.h>
>  #include <linux/vmalloc.h>
> +#include <linux/crash_dump.h>
>  
>  struct iommu_dma_msi_page {
>  	struct list_head	list;
> @@ -351,6 +352,21 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>  	return iova_reserve_iommu_regions(dev, domain);
>  }
>  
> +static int handle_deferred_device(struct device *dev,
> +	struct iommu_domain *domain)
> +{
> +	const struct iommu_ops *ops = domain->ops;
> +
> +	if (!is_kdump_kernel())
> +		return 0;
> +
> +	if (unlikely(ops->is_attach_deferred &&
> +		ops->is_attach_deferred(domain, dev)))
> +		return iommu_attach_device(domain, dev);
> +
> +	return 0;
> +}
> +
>  /**
>   * dma_info_to_prot - Translate DMA API directions and attributes to IOMMU API
>   *                    page flags.
> @@ -463,6 +479,9 @@ static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
>  	size_t iova_off = iova_offset(iovad, phys);
>  	dma_addr_t iova;
>  
> +	if (unlikely(handle_deferred_device(dev, domain)))
> +		return DMA_MAPPING_ERROR;
> +
>  	size = iova_align(iovad, size + iova_off);
>  
>  	iova = iommu_dma_alloc_iova(domain, size, dma_get_mask(dev), dev);

iommu_map_atomic() is applied to __iommu_dma_map() in 2/5.
Is it an atomic context currently given the mutex_lock() in
iommu_attach_device()?

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