Re: [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver

[Tianyu Lan <ltykernel@xxxxxxxxx>]

On 8/20/2021 11:20 PM, Tianyu Lan wrote:
> > The whole approach here is to do dma remapping on each individual page
> > of the I/O buffer.  But wouldn't it be possible to use dma_map_sg() to 
> > map
> > each scatterlist entry as a unit?  Each scatterlist entry describes a 
> > range of
> > physically contiguous memory.  After dma_map_sg(), the resulting dma
> > address must also refer to a physically contiguous range in the swiotlb
> > bounce buffer memory.   So at the top of the "for" loop over the 
> > scatterlist
> > entries, do dma_map_sg() if we're in an isolated VM.  Then compute the
> > hvpfn value based on the dma address instead of sg_page().  But 
> > everything
> > else is the same, and the inner loop for populating the pfn_arry is 
> > unmodified.
> > Furthermore, the dma_range array that you've added is not needed, since
> > scatterlist entries already have a dma_address field for saving the 
> > mapped
> > address, and dma_unmap_sg() uses that field.
> I don't use dma_map_sg() here in order to avoid introducing one more 
> loop(e,g dma_map_sg()). We already have a loop to populate 
> cmd_request->dma_range[] and so do the dma map in the same loop.
Sorry for a typo. s/cmd_request->dma_range[]/payload->range.pfn_array[]/