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Date:   Thu, 4 Feb 2021 09:40:23 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Dongli Zhang <dongli.zhang@oracle.com>
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Subject: Re: [PATCH RFC v1 5/6] xen-swiotlb: convert variables to arrays
Message-ID: <20210204084023.GA32328@lst.de>
References: <20210203233709.19819-1-dongli.zhang@oracle.com> <20210203233709.19819-6-dongli.zhang@oracle.com>
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So one thing that has been on my mind for a while:  I'd really like
to kill the separate dma ops in Xen swiotlb.  If we compare xen-swiotlb
to swiotlb the main difference seems to be:

 - additional reasons to bounce I/O vs the plain DMA capable
 - the possibility to do a hypercall on arm/arm64
 - an extra translation layer before doing the phys_to_dma and vice
   versa
 - an special memory allocator

I wonder if inbetween a few jump labels or other no overhead enablement
options and possibly better use of the dma_range_map we could kill
off most of swiotlb-xen instead of maintaining all this code duplication?