Re: [PATCH V5 00/22] IOREQ feature (+ virtio-mmio) on Arm

[Julien Grall <julien@xxxxxxx>]

Hi,

On 25/01/2021 19:08, Oleksandr Tyshchenko wrote:
 > Patch series [8] was rebased on recent "staging branch"
> (5e31789 tools/ocaml/libs/xb: Do not crash after xenbus is unmapped) and tested 
> on
> Renesas Salvator-X board + H3 ES3.0 SoC (Arm64) with virtio-mmio disk backend 
> [9]
> running in driver domain and unmodified Linux Guest running on existing
> virtio-blk driver (frontend). No issues were observed. Guest domain 
> 'reboot/destroy'
> use-cases work properly. Patch series was only build-tested on x86.
I have done basic testing with a Linux guest on x86 and I didn't spot 
any regression.
Unfortunately, I don't have a Windows VM in hand, so I can't confirm if 
there is no regression there. Can anyone give a try?
On a separate topic, Andrew expressed on IRC some concern to expose the 
bufioreq interface to other arch than x86. I will let him explain his 
view here.
Given that IOREQ will be a tech preview on Arm (this implies the 
interface is not stable) on Arm, I think we can defer the discussion 
past the freeze.
For now, I would suggest to check if a Device Model is trying to create 
an IOREQ server with bufioreq is enabled (see ioreq_server_create()). 
This would not alleviate Andrew's concern, however it would at allow us 
to judge whether the buffering concept is going to be used on Arm (I can 
see some use for the Virtio doorbell).
What do others think?

Cheers,

--
Julien Grall