linux-kernel - Re: [PATCH v10 10/12] swiotlb: Add restricted DMA alloc/free support

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Date:   Tue, 15 Jun 2021 15:42:08 +0200
From:   Christoph Hellwig <hch@....de>
To:     Claire Chang <tientzu@...omium.org>
Cc:     Rob Herring <robh+dt@...nel.org>, mpe@...erman.id.au,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        boris.ostrovsky@...cle.com, jgross@...e.com,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        benh@...nel.crashing.org, paulus@...ba.org,
        "list@....net:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        sstabellini@...nel.org, Robin Murphy <robin.murphy@....com>,
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        Thierry Reding <treding@...dia.com>, mingo@...nel.org,
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        Greg KH <gregkh@...uxfoundation.org>,
        Saravana Kannan <saravanak@...gle.com>,
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        thomas.hellstrom@...ux.intel.com
Subject: Re: [PATCH v10 10/12] swiotlb: Add restricted DMA alloc/free
 support

On Tue, Jun 15, 2021 at 09:27:09PM +0800, Claire Chang wrote:
> Add the functions, swiotlb_{alloc,free} to support the memory allocation
> from restricted DMA pool.
> 
> The restricted DMA pool is preferred if available.
> 
> Note that since coherent allocation needs remapping, one must set up
> another device coherent pool by shared-dma-pool and use
> dma_alloc_from_dev_coherent instead for atomic coherent allocation.

Note: when applied this should go before the next patch to make sure
bisection works fine.

>  #ifdef CONFIG_DMA_RESTRICTED_POOL
> +struct page *swiotlb_alloc(struct device *dev, size_t size)
> +{
> +	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
> +	phys_addr_t tlb_addr;
> +	int index;
> +
> +	/*
> +	 * Skip io_tlb_default_mem since swiotlb_alloc doesn't support atomic
> +	 * coherent allocation. Otherwise might break existing devices.
> +	 * One must set up another device coherent pool by shared-dma-pool and
> +	 * use dma_alloc_from_dev_coherent instead for atomic coherent
> +	 * allocation to avoid mempry remapping.

s/mempry/memory/g

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@....de>