Re: [PATCH 01/21] arm64/iommu: handle non-remapped addresses in ->mmap and ->get_sgtable

[Robin Murphy <robin.murphy@arm.com>]

On 27/03/2019 08:04, Christoph Hellwig wrote:
> DMA allocations that can't sleep may return non-remapped addresses, but
> we do not properly handle them in the mmap and get_sgtable methods.
> Resolve non-vmalloc addresses using virt_to_page to handle this corner
> case.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   arch/arm64/mm/dma-mapping.c | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index 78c0a72f822c..be88beb2e377 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -249,6 +249,11 @@ static int __iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
>   	if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
>   		return ret;
>   
> +	if (!is_vmalloc_addr(cpu_addr)) {
> +		unsigned long pfn = page_to_pfn(virt_to_page(cpu_addr));
> +		return __swiotlb_mmap_pfn(vma, pfn, size);
> +	}
> +
>   	if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
>   		/*
>   		 * DMA_ATTR_FORCE_CONTIGUOUS allocations are always remapped,
> @@ -272,10 +277,15 @@ static int __iommu_get_sgtable(struct device *dev, struct sg_table *sgt,
>   	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
>   	struct vm_struct *area = find_vm_area(cpu_addr);
>   
> +	if (!is_vmalloc_addr(cpu_addr)) {
> +		struct page *page = virt_to_page(cpu_addr);
> +		return __swiotlb_get_sgtable_page(sgt, page, size);
> +	}
> +
>   	if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
>   		/*
>   		 * DMA_ATTR_FORCE_CONTIGUOUS allocations are always remapped,
> -		 * hence in the vmalloc space.
> +		 *  hence in the vmalloc space.

Without this bit ^^,

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

>   		 */
>   		struct page *page = vmalloc_to_page(cpu_addr);
>   		return __swiotlb_get_sgtable_page(sgt, page, size);
>