linux-kernel - Re: [rfc 5/6] dma-direct: atomic allocations must come from unencrypted pools

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Date:   Tue, 10 Mar 2020 19:47:41 +0100
From:   Christoph Hellwig <hch@....de>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Christoph Hellwig <hch@....de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Singh, Brijesh" <brijesh.singh@....com>,
        "Grimm, Jon" <jon.grimm@....com>, Joerg Roedel <joro@...tes.org>,
        baekhw@...gle.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: Re: [rfc 5/6] dma-direct: atomic allocations must come from
 unencrypted pools

On Fri, Mar 06, 2020 at 04:36:07PM -0800, David Rientjes wrote:
> As a preliminary change to this series, I could move the atomic pools and 
> coherent_pool command line to a new kernel/dma/atomic_pools.c file with a 
> new CONFIG_DMA_ATOMIC_POOLS that would get "select"ed by CONFIG_DMA_REMAP 
> and CONFIG_AMD_MEM_ENCRYPT and call into dma_common_contiguous_remap() if 
> we have CONFIG_DMA_DIRECT_REMAP when adding pages to the pool.

Yes.  Although I'd just name it kernel/dma/pool.c and
CONFIG_DMA_COHERENT_POOL or so, as I plan to reuse the code for
architectures that just preallocate all coherent memory at boot time
as well.

> I think that's what you mean by splitting the pool from remapping, 
> otherwise we still have a full CONFIG_DMA_REMAP dependency here.  If you 
> had something else in mind, please let me know.  Thanks!

Yes, that is exactly what I meant.