From: Julien Grall <julien@xen.org>
To: Ian Jackson <ian.jackson@citrix.com>
Cc: Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
Paul Durrant <paul@xen.org>,
Andrew Cooper <Andrew.Cooper3@citrix.com>,
Julien Grall <jgrall@amazon.com>,
George Dunlap <George.Dunlap@citrix.com>,
"committers@xenproject.org" <committers@xenproject.org>,
Jan Beulich <jbeulich@suse.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Roger Pau Monne <roger.pau@citrix.com>,
Julien Grall <julien.grall.oss@gmail.com>
Subject: Re: [PATCH v3 for-4.14] pvcalls: Document correctly and explicitely the padding for all arches
Date: Fri, 26 Jun 2020 18:46:12 +0100 [thread overview]
Message-ID: <8335fa07-7610-2a40-36fc-49d6f900026c@xen.org> (raw)
In-Reply-To: <24307.16713.764272.855818@mariner.uk.xensource.com>
Hi Ian,
Thank you for your input!
On 24/06/2020 13:04, Ian Jackson wrote:
> Julien Grall writes ("Re: [PATCH v3 for-4.14] pvcalls: Document correctly and explicitely the padding for all arches"):
>> (+ Committers)
> ...
>> As Jan and you disagree on the approach, I would like to get more input.
>>
>> To summarize the discussion, the document for PV calls and the public
>> headers don't match when describing the padding. There is a disagreement
>> on which of the two are the authority and therefore which one to fix.
>>
>> Does anyone else have a preference on the approach?
>
> Hi.
>
>> [Jan:]
>>> I am leaning towards the header as authoritative because this has
>>> always been the case in the past and nothing in xen.git says
>>> otherwise. However I am not a user of pvcalls, so I don't really have
>>> any big incentive to go either way.
>
> I think the practice of using headers as protocol specs is not a
> particularly good one. Certainly my expectations anywhere outside the
> Xen Project is that if there's a doc, that is at the very least on par
> with any header file. Of course there are possible compatibility
> implications:
>
>> Yeah, we are risking breaking one set of users either way :-/
>> In reality, we are using pvcalls on arm64 in a new project (but it is
>> still very green). I am not aware of anybody using pvcalls on x86
>> (especially x86_32).
>>
>> I would prefer to honor the pvcalls.pandoc specification because that is
>> what it was meant to be, and also leads to a better protocol
>> specification.
>
> pvcalls in Linux is Tech Preview / Experimental AFAICT ? I think that
> means we can de jure change things like this.
SUPPORT.md suggests this is a Tech Preview, so I agree that we could
still change the interface.
>
> And it seems that we don't think there are any actual users who would
> experience compatibility problems.
Right, that's what Stefano suggested.
>
> So I don't think the compatibility concerns are a reason not to change
> the header rather than the document.
>
> So I think my conclusion is the same as Julien's: we should change the
> header to match the doc.
Ok, so you are on the same page as Stefano. I will revert to the v1
change and rework the commit message then.
>
>>>> For the future, I would highly suggest writing down the support
>>>> decision in xen.git. This would avoid such debate on what is the
>>>> authority...
>>>
>>> Yes that's the way to go
>
> Maybe it would be worth putting a note somewhere in the headers saying
> the headers are provided for convenience but that the ABIs and
> protocols are as specified in the docs (at least where docs exist).
I will write a patch for it.
Cheers,
--
Julien Grall
next prev parent reply other threads:[~2020-06-26 17:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-13 18:41 [PATCH v3 for-4.14] pvcalls: Document correctly and explicitely the padding for all arches Julien Grall
2020-06-15 8:26 ` Paul Durrant
2020-06-16 1:00 ` Stefano Stabellini
2020-06-16 7:13 ` Jan Beulich
2020-06-16 9:39 ` Julien Grall
2020-06-16 20:57 ` Stefano Stabellini
2020-06-16 21:31 ` Julien Grall
2020-06-18 1:34 ` Stefano Stabellini
2020-06-18 15:00 ` Julien Grall
2020-06-24 11:29 ` [INPUT REQUESTED][PATCH " Julien Grall
2020-06-24 12:05 ` Ian Jackson
2020-06-24 12:04 ` [PATCH " Ian Jackson
2020-06-26 17:46 ` Julien Grall [this message]
2020-06-16 8:26 ` Jan Beulich
2020-06-16 9:19 ` Julien Grall
2020-06-16 9:36 ` Jan Beulich
2020-06-16 9:42 ` Julien Grall
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