Re: [PATCH v3] xen: Allow a default compiled-in command line using Kconfig

From: Zhongze Liu <blackskygg@gmail.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	Julien Grall <julien.grall@arm.com>,
	Doug Goldstein <cardoe@cardoe.com>,
	Jan Beulich <JBeulich@suse.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v3] xen: Allow a default compiled-in command line using Kconfig
Date: Wed, 8 Mar 2017 15:16:29 +0800	[thread overview]
Message-ID: <CAHrd_jpQveSfW8Dbd6VnKt11df7BpL1XzZAzAS5dnT4vppKLiA@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1703071333380.17906@sstabellini-ThinkPad-X260>

So, taking all of the conversations above into consideration, the
following changes
should be done to this patch:

1. According to Andrew and Jan's suggestions, I'll remove the
CMDLINE_BOOL option,
    and deal with CMDLINE without the #ifdef-ary's.

2. Make the option CMDLINE_OVERRIDE depends on EXPERT.

3. Move the duplicated code in the various setup.c's into
common/kernel.c; Introduce a wrapper
    to common/kernel.c:cmdline_parse(), and let that wrapper
automatically deal with CONFIG_CMDLINE,
    so the start_xen()'s won't be bothered to do the concatenation by
themselves.

4. As for the different behavior between arm and x86 on handling the
dom0 options after " -- " in the
    command line, I will left this difference as untouched, coz
whether to add this feature to arm or to remove
    this feature from x86 is beyond the scope of this patch.

But there's one thing that I'm not quite sure. Since currently there
isn't any cumulative options in
Xen, I just can't deal with them - Jan?

2017-03-08 5:37 GMT+08:00 Stefano Stabellini <sstabellini@kernel.org>:
> On Tue, 7 Mar 2017, Julien Grall wrote:
>> Hi Stefano,
>>
>> On 03/07/2017 07:54 PM, Stefano Stabellini wrote:
>> > On Tue, 7 Mar 2017, Julien Grall wrote:
>> > Given that upstream GRUB doesn't yet support booting Xen on ARM (without
>> > any additional patches), I think that the ability to completely change
>> > the command line from the EFI shell would be useful. Besides, although
>> > it is not mandatory, I think it would be best not to unnecessarily
>> > diverge from x86 in terms of EFI booting.
>>
>> I don't consider x86 solution as granted for ARM, and I would have thought it
>> was the same on your side given the change you requested for dom0_mem
>> recently.
>
> I agree. I am only saying that all things being equal, we might as well
> keep compatibility. If nothing else, it will be easier to write docs.
> The dom0_mem case is an example where things are not equal between x86
> and arm, but the parameter still works similarly across the two archs.
>
>
>> I still don't see a reason to override the command line option as usually the
>> issue will not be because of the command line but the kernel itself. At least
>> this is my experience on ARM so far.
>
> I think it can be useful, even just for tests, especially given that
> grub is still unable to boot Xen.
>
>
>> Anyway, I am not going to argue on this. If you think it should be done, then
>> it should be in a separate patch.
>
> That would be best.

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