linux-kernel - Re: [PATCH V5 12/12] net: netvsc: Add Isolation VM support for netvsc driver

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Message-ID: <20210928053911.GA29208@lst.de>
Date:   Tue, 28 Sep 2021 07:39:11 +0200
From:   Christoph Hellwig <hch@....de>
To:     Tianyu Lan <ltykernel@...il.com>
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Subject: Re: [PATCH V5 12/12] net: netvsc: Add Isolation VM support for
 netvsc driver

On Mon, Sep 27, 2021 at 10:26:43PM +0800, Tianyu Lan wrote:
> Hi Christoph:
>     Gentile ping. The swiotlb and shared memory mapping changes in this
> patchset needs your reivew. Could you have a look?

I'm a little too busy for a review of such a huge patchset right now.
That being said here are my comments from a very quick review:

 - the bare memremap usage in swiotlb looks strange and I'd
   definitively expect a well documented wrapper.
 - given that we can now hand out swiotlb memory for coherent mappings
   we need to carefully audit what happens when this memremaped
   memory gets mmaped or used through dma_get_sgtable
 - the netscv changes I'm not happy with at all.  A large part of it
   is that the driver already has a bad structure, but this series
   is making it significantly worse.  We'll need to find a way
   to use the proper dma mapping abstractions here.  One option
   if you want to stick to the double vmapped buffer would be something
   like using dma_alloc_noncontigous plus a variant of
   dma_vmap_noncontiguous that takes the shared_gpa_boundary into
   account.