linux-kernel - Re: [RFC KERNEL PATCH v2 1/3] xen/pci: Add xen_reset_device

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Date:   Tue, 05 Dec 2023 18:02:54 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Stefano Stabellini <sstabellini@...nel.org>,
        "Chen, Jiqian" <Jiqian.Chen@....com>
Cc:     Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Roger Pau Monné <roger.pau@...rix.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "Stabellini, Stefano" <stefano.stabellini@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Hildebrand, Stewart" <Stewart.Hildebrand@....com>,
        "Ragiadakou, Xenia" <Xenia.Ragiadakou@....com>,
        "Huang, Honglei1" <Honglei1.Huang@....com>,
        "Zhang, Julia" <Julia.Zhang@....com>,
        "Huang, Ray" <Ray.Huang@....com>
Subject: Re: [RFC KERNEL PATCH v2 1/3] xen/pci: Add xen_reset_device_state
 function

On Mon, Dec 04 2023 at 13:31, Stefano Stabellini wrote:
> On Mon, 3 Dec 2023, Chen, Jiqian wrote:
>> >> vpci device state when device is reset on dom0 side.
>> >>
>> >> And call that function in pcistub_init_device. Because when
>> >> we use "pci-assignable-add" to assign a passthrough device in
>> >> Xen, it will reset passthrough device and the vpci state will
>> >> out of date, and then device will fail to restore bar state.
>> >>
>> >> Signed-off-by: Jiqian Chen <Jiqian.Chen@....com>
>> >> Signed-off-by: Huang Rui <ray.huang@....com>
>> > 
>> > This Signed-off-by chain is incorrect.
>> > 
>> > Documentation/process/submitting-patches.rst has a full chapter about
>> > S-O-B and the correct usage.
>> I am the author of this series of patches, and Huang Rui transported the v1 to upstream. And now I transport v2. I am not aware that the SOB chain is incorrect.
>> Do you have any suggestions?
>
> I think he means that your Signed-off-by should be the second one of the
> two as you are the one submitting the patch to the LKML

No.

   Mailfrom: Jiqian Chen <Jiqian.Chen@....com>
   <body>

   Changelog-text

   Signed-off-by: Huang Rui <ray.huang@....com>
   Signed-off-by: Jiqian Chen <Jiqian.Chen@....com>

is equally wrong because that would end up with Chen as author and Huang
as first S-O-B which is required to be the author's S-O-B

To make the above correct this would require:

   Mailfrom: Jiqian Chen <Jiqian.Chen@....com>
   <body>

   From: Huang Rui <ray.huang@....com>

   Changelog-text

   Signed-off-by: Huang Rui <ray.huang@....com>
   Signed-off-by: Jiqian Chen <Jiqian.Chen@....com>

   which tells that Huang is the author and Chen is the 'transporter',
   which unfortunately does not reflect reality.

Or:

   Mailfrom: Jiqian Chen <Jiqian.Chen@....com>
   <body>

   Changelog-text

   Co-developed-by: Huang Rui <ray.huang@....com>
   Signed-off-by: Huang Rui <ray.huang@....com>
   Signed-off-by: Jiqian Chen <Jiqian.Chen@....com>

   which tells that Checn is the author and Huang co-developed the
   patch, which might be true or not.


V1 which was sent by Huang has the ordering is correct:

   Mailfrom: Huang Rui <ray.huang@....com>
   <body>

   From: Jiqian Chen <Jiqian.Chen@....com>

   Changelog-text

   Signed-off-by: Jiqian Chen <Jiqian.Chen@....com>
   Signed-off-by: Huang Rui <ray.huang@....com>

   i.e. Chen authored and Huang transported

Now this V2 has not really much to do with V1 and is a new
implementation to solve the problem, which was authored by Chen, so
Huang is not involved at all if I understand correctly.

So what does his S-O-B mean here? Nothing...

It's very well documented how the whole S-O-B business works and it's
not really rocket science to get it straight.

It has a meaning and is not just for decoration purposes.

Thanks,

        tglx