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


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 
Renesas Salvator-X board + H3 ES3.0 SoC (Arm64) with virtio-mmio disk backend 
running in driver domain and unmodified Linux Guest running on existing
virtio-blk driver (frontend). No issues were observed. Guest domain 
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?


Julien Grall



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