linux-kernel - Re: [PATCH v6 00/17] Introduce SCMI transport based on VirtIO

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Message-ID: <YROY6YntswWxfaub@google.com>
Date:   Wed, 11 Aug 2021 09:31:21 +0000
From:   Floris Westermann <westermann@...gle.com>
To:     Cristian Marussi <cristian.marussi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, sudeep.holla@....com,
        james.quinlan@...adcom.com, Jonathan.Cameron@...wei.com,
        f.fainelli@...il.com, etienne.carriere@...aro.org,
        vincent.guittot@...aro.org, souvik.chakravarty@....com,
        igor.skalkin@...nsynergy.com, peter.hilber@...nsynergy.com,
        alex.bennee@...aro.org, jean-philippe@...aro.org,
        mikhail.golubev@...nsynergy.com, anton.yakovlev@...nsynergy.com,
        Vasyl.Vavrychuk@...nsynergy.com,
        Andriy.Tryshnivskyy@...nsynergy.com
Subject: Re: [PATCH v6 00/17] Introduce SCMI transport based on VirtIO

Hi Cristian,

I am currently working on an interface for VMs to communicate their
performance requirements to the hosts by passing through cpu frequency
adjustments.

Your patch looks very interesting but I have some questions:


On Mon, Jul 12, 2021 at 03:18:16PM +0100, Cristian Marussi wrote:
>
> The series has been tested using an emulated fake SCMI device and also a
> proper SCP-fw stack running through QEMU vhost-users, with the SCMI stack
> compiled, in both cases, as builtin and as a loadable module, running tests
> against mocked SCMI Sensors using HWMON and IIO interfaces to check the
> functionality of notifications and sync/async commands.
>
> Virtio-scmi support has been exercised in the following testing scenario
> on a JUNO board:
>
>  - normal sync/async command transfers
>  - notifications
>  - concurrent delivery of correlated response and delayed responses
>  - out-of-order delivery of delayed responses before related responses
>  - unexpected delayed response delivery for sync commands
>  - late delivery of timed-out responses and delayed responses
>
> Some basic regression testing against mailbox transport has been performed
> for commands and notifications too.
>
> No sensible overhead in total handling time of commands and notifications
> has been observed, even though this series do indeed add a considerable
> amount of code to execute on TX path.
> More test and measurements could be needed in these regards.
>

Can you share any data and benchmarks using you fake SCMI device.
Also, could you provide the emulated device code so that the results can
be reproduced.


Cheers,
Floris