Re: [Xen-devel] [PATCH v2 4/6] x86/boot: Rename trampoline_{start, end} to boot_trampoline_{start, end}

From: Jan Beulich <jbeulich@suse.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	xen-devel <xen-devel@lists.xenproject.org>,
	"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v2 4/6] x86/boot: Rename trampoline_{start, end} to boot_trampoline_{start, end}
Date: Tue, 27 Aug 2019 10:51:10 +0200	[thread overview]
Message-ID: <69fad9d8-dd8f-0982-3b87-de83be5b2ae2@suse.com> (raw)
In-Reply-To: <35a8cd053ddf7129808c9e2755c4e7fe0d1a5c60.camel@infradead.org>

On 19.08.2019 17:24, David Woodhouse wrote:
> On Mon, 2019-08-12 at 11:55 +0200, Jan Beulich wrote:
>> On 09.08.2019 17:02, David Woodhouse wrote:
>>> From: David Woodhouse <dwmw@amazon.co.uk>
>>>
>>> In preparation for splitting the boot and permanent trampolines from
>>> each other. Some of these will change back, but most are boot so do the
>>> plain search/replace that way first, then a subsequent patch will extract
>>> the permanent trampoline code.
>>
>> To be honest I don't view it as helpful to do things in this order.
>> If you first re-arranged the ordering of items within the trampoline,
>> we'd then not end up with an intermediate state where the labels are
>> misleading. Is there a reason things can't sensibly be done the other
>> way around?
> 
> Obviously I did all this in a working tree first, swore at it a lot and
> finally got it working, then attempted to split it up into separate
> meaningful commits which individually made sense. There is plenty of
> room for subjectivity in the choices I made in that last step.
> 
> I'm not sure I quite see why you say the labels are misleading. My
> intent was to apply labels based on what each object is *used* for,
> despite the fact that to start with they're all actually in the same
> place. And then to actually move each different type of symbol into its
> separate section/location to clean things up.
> 
> Is it just the code comments at the start of trampoline.S that you find
> misleading in the interim stage? Because those *don't* purely talk
> about what bootsym/bootdatasym/trampsym/tramp32sym are used for; they
> do say how they are (eventually) relocated. I suppose I could rip that
> code comment out of patch #3 completely and add it again in a later
> commit... or just just add it again. I write code comments in an
> attempt to be helpful to those who come after me (especially when
> that's actually myself) but if they're going to cause problems, then
> maybe they're more hassle than they're worth?

No, it's actually the label names: The "boot" that this patch prefixes
to them isn't correct until all post-boot (i.e. AP bringup) parts
have been moved out of the framed block of code.

Jan

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