linux-kernel - Regression due to d98849aff879 (dma-direct: handle DMA_ATTR_NO_KERNEL

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Message-ID: <1565082809.2323.24.camel@pengutronix.de>
Date:   Tue, 06 Aug 2019 11:13:29 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Christoph Hellwig <hch@....de>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Regression due to d98849aff879 (dma-direct: handle
 DMA_ATTR_NO_KERNEL_MAPPING in common code)

Hi Christoph,

I just found a regression where my NVMe device is no longer able to set
up its HMB.

After subject commit dma_direct_alloc_pages() is no longer initializing
dma_handle properly when DMA_ATTR_NO_KERNEL_MAPPING is set, as the
function is now returning too early.

Now this could easily be fixed by adding the phy_to_dma translation to
the NO_KERNEL_MAPPING code path, but I'm not sure how this stuff
interacts with the memory encryption stuff set up later in the
function, so I guess this should be looked at by someone with more
experience with this code than me.

Regards,
Lucas