Messages in this thread | | | Subject | Re: [PATCH 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver | From | Tianyu Lan <> | Date | Mon, 2 Aug 2021 22:08:43 +0800 |
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On 8/2/2021 9:20 PM, Joerg Roedel wrote: > On Wed, Jul 28, 2021 at 10:52:28AM -0400, Tianyu Lan wrote: >> In Isolation VM, all shared memory with host needs to mark visible >> to host via hvcall. vmbus_establish_gpadl() has already done it for >> storvsc rx/tx ring buffer. The page buffer used by vmbus_sendpacket_ >> mpb_desc() still need to handle. Use DMA API to map/umap these >> memory during sending/receiving packet and Hyper-V DMA ops callback >> will use swiotlb function to allocate bounce buffer and copy data >> from/to bounce buffer. > > I am wondering why you dont't use DMA-API unconditionally? It provides > enough abstraction to do the right thing for isolated and legacy VMs. >
In VMbus, there is already a similar bounce buffer design and so there is no need to call DMA-API for such buffer. Calling DMA-API is to use swiotlb bounce buffer for those buffer which hasn't been covered. This is why need to conditionally call DMA API.
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