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Date: Tue, 7 Nov 2017 09:03:29 -0700
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Christoph Hellwig <hch@infradead.org>
Cc: "Wei Hu (Xavier)" <xavier.huwei@huawei.com>,
        Robin Murphy <robin.murphy@arm.com>, Leon Romanovsky <leon@kernel.org>,
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Subject: Re: [PATCH for-next 2/4] RDMA/hns: Add IOMMU enable support in hip08
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On Tue, Nov 07, 2017 at 07:58:05AM -0800, Christoph Hellwig wrote:
> On Tue, Nov 07, 2017 at 08:48:38AM -0700, Jason Gunthorpe wrote:
> > Can't you just use vmalloc and dma_map that? Other drivers follow that
> > approach..
> 
> You can't easily due to the flushing requirements.  We used to do that
> in XFS and it led to problems.  You need the page allocator + vmap +
> invalidate_kernel_vmap_range + flush_kernel_vmap_range to get the
> cache flushing right.

Yes, exactly something ugly like that.. :\

Jason