[GEDI] [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint

David Hildenbrand david at redhat.com
Tue Aug 23 08:01:59 UTC 2022

On 23.08.22 00:24, Stefan Hajnoczi wrote:
> Register guest RAM using BlockRAMRegistrar and set the
> BDRV_REQ_REGISTERED_BUF flag so block drivers can optimize memory
> accesses in I/O requests.
> This is for vdpa-blk, vhost-user-blk, and other I/O interfaces that rely
> on DMA mapping/unmapping.

Can you explain why we're monitoring RAMRegistrar to hook into "guest
RAM" and not go the usual path of the MemoryListener?

What will BDRV_REQ_REGISTERED_BUF actually do? Pin all guest memory in
the worst case such as io_uring fixed buffers would do ( I hope not ).


David / dhildenb

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