Re: [PATCH 3/5] hyperv/IOMMU: Enable swiotlb bounce buffer for Isolation VM

From: Tianyu Lan
Date: Fri Nov 19 2021 - 09:24:01 EST

On 11/17/2021 10:00 PM, Tianyu Lan wrote:
On 11/17/2021 6:01 PM, Christoph Hellwig wrote:
This doesn't really have much to do with normal DMA mapping,
so why does this direct through the dma ops?

According to the previous discussion, dma_alloc_noncontigous()
and dma_vmap_noncontiguous() may be used to handle the noncontigous
memory alloc/map in the netvsc driver. So add alloc/free and vmap/vunmap
callbacks here to handle the case. The previous patch v4 & v5 handles
the allocation and map in the netvsc driver. If this should not go though dma ops, We also may make it as vmbus specific function and keep
the function in the vmbus driver.

Hi Christoph:
Sorry to bother you. Could you have a look? Which solution do you
prefer? If we need to call dma_alloc/map_noncontigous() function in the
netvsc driver what patch 4 does. The Hyper-V specific implementation
needs to be hided in some callbacks and call these callback in the
dma_alloc/map_noncontigous(). I used dma ops here. If the allocation and
map operation should be Hyper-V specific function, we may put these
functions in the vmbus driver and other vmbus device drivers also may
reuse these functions if necessary.