Re: [RFC 0/8] blkio: add libblkio BlockDriver

[Stefano Garzarella]

On Wed, Mar 23, 2022 at 11:17:19AM +0000, Stefan Hajnoczi wrote:
> This patch series adds a QEMU BlockDriver for libblkio
> (https://gitlab.com/libblkio/libblkio/), a library for high-performance block
> device I/O. Currently libblkio has basic io_uring support with additional
> drivers in development.
>
> The first patch adds the core BlockDriver and most of the libblkio API usage.
> The remainder of the patch series reworks the existing QEMU bdrv_register_buf()
> API so virtio-blk emulation efficiently map guest RAM for libblkio - some
> libblkio drivers require that I/O buffer memory is pre-registered (think VFIO,
> vhost, etc).
>
> This block driver is incomplete because bdrv_refresh_limits() and several other
> APIs are not yet implemented. You can already boot a guest though. Once the
> missing gaps have been filled in I will send a non-RFC patch series.
>
> Regarding the design: each libblkio driver is a separately named BlockDriver.
> That means there is an "io_uring" BlockDriver and not a generic "libblkio"
> BlockDriver. In the future there will be additional BlockDrivers, all defined
> in block/blkio.c. This way QAPI and open parameters are type-safe and mandatory
> parameters can be checked by QEMU.

Indeed it was a great design. Adding the "vhost_vdpa" driver was quick 
and easy.

I've been reviewing and testing it. Aside from the problem in patch 7, 
the rest already looks good to me.

Thanks,
Stefano