linux-kernel - Re: [PATCH v2 7/9] dpaa_eth: fix iova handling for contiguous frames

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Message-ID: <20190427164612.GA12450@infradead.org>
Date:   Sat, 27 Apr 2019 09:46:12 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     laurentiu.tudor@....com
Cc:     netdev@...r.kernel.org, madalin.bucur@....com, roy.pledge@....com,
        camelia.groza@....com, leoyang.li@....com,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linuxppc-dev@...ts.ozlabs.org, davem@...emloft.net,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 7/9] dpaa_eth: fix iova handling for contiguous frames

On Sat, Apr 27, 2019 at 10:10:29AM +0300, laurentiu.tudor@....com wrote:
> From: Laurentiu Tudor <laurentiu.tudor@....com>
> 
> The driver relies on the no longer valid assumption that dma addresses
> (iovas) are identical to physical addressees and uses phys_to_virt() to
> make iova -> vaddr conversions. Fix this by adding a function that does
> proper iova -> phys conversions using the iommu api and update the code
> to use it.
> Also, a dma_unmap_single() call had to be moved further down the code
> because iova -> vaddr conversions were required before the unmap.
> For now only the contiguous frame case is handled and the SG case is
> split in a following patch.
> While at it, clean-up a redundant dpaa_bpid2pool() and pass the bp
> as parameter.

Err, this is broken.  A driver using the DMA API has no business
call IOMMU APIs.  Just save the _virtual_ address used for the mapping
away and use that again.  We should not go through crazy gymnastics
like this.