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

On 9/28/2021 1:39 PM, Christoph Hellwig wrote:

On Mon, Sep 27, 2021 at 10:26:43PM +0800, Tianyu Lan wrote:

quoted

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.