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

[Tianyu Lan]

On 9/28/2021 1:39 PM, Christoph Hellwig wrote:
> 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:
Hi Christoph:
      Thanks for your comments. Most patches in the series are Hyper-V
change. I will split patchset and make it easy to review.


>   - the bare memremap usage in swiotlb looks strange and I'd
>     definitively expect a well documented wrapper.

OK. Should the wrapper in the DMA code? How about dma_map_decrypted() 
introduced in the V4?
https://lkml.org/lkml/2021/8/27/605

>   - 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

OK. I check that.

>   - 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.

OK. I will do that.