Re: [PATCH v2 20/21] xen: support console_switching between Dom0 and DomUs on ARM

From: George Dunlap <George.Dunlap@citrix.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: Stefano Stabellini <stefanos@xilinx.com>,
	Wei Liu <wei.liu2@citrix.com>,
	Andrew Cooper <Andrew.Cooper3@citrix.com>,
	"Tim (Xen.org)" <tim@xen.org>,
	George Dunlap <George.Dunlap@citrix.com>,
	xen-devel <xen-devel@lists.xen.org>,
	Julien Grall <julien.grall@arm.com>,
	Jan Beulich <JBeulich@suse.com>,
	Ian Jackson <Ian.Jackson@citrix.com>,
	"andrii_anisov@epam.com" <andrii_anisov@epam.com>,
	"nd@arm.com" <nd@arm.com>
Subject: Re: [PATCH v2 20/21] xen: support console_switching between Dom0 and DomUs on ARM
Date: Wed, 18 Jul 2018 20:37:44 +0000	[thread overview]
Message-ID: <1AB57DFE-53DF-40A0-8CAD-89EFFDC8A422@citrix.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1807180952580.21200@sstabellini-ThinkPad-X260>

> On Jul 18, 2018, at 1:01 PM, Stefano Stabellini <sstabellini@kernel.org> wrote:
> 
> On Wed, 18 Jul 2018, Jan Beulich wrote:
>>>>> On 17.07.18 at 22:29, <julien.grall@arm.com> wrote:
>>> On 07/07/2018 00:12, Stefano Stabellini wrote:
>>>> Today Ctrl-AAA is used to switch between Xen and Dom0. Extend the
>>>> mechanism to allow for switching between Xen, Dom0, and any of the
>>>> initial DomU created from Xen alongside Dom0 out of information provided
>>>> via device tree.
>>> It feels a bit painful for the user to switch N times to get his domain 
>>> console. Would it be possible to provide a new key binding where you 
>>> type the domain ID you want to switch to?
>> 
>> Does that mean you'd want to use 0-9 for this purpose? I'd be
>> very hesitant to accept such, as we're pretty tight with available
>> characters already. And of course 0-9 wouldn't scale to Dom10
>> and beyond. If you have something else in mind, I think it would
>> help if you spelled this out.
> 
> Let me premise that I think this is not important and the solution will
> be fine even only with the existing Ctrl-AAA switching mechanism. In
> fact, I would add that any usability improvements should NOT be part of
> this series. I think we have more important things to add now before we
> get to the console switching mechanism.
> 
> Let me also premise that the number of guests I imagine will be booted
> using dom0less today is actually very limited. I doubt more than 4
> guests. So it would be tolerable to rotate between them using Ctrl-AAA.
> 
> 
> That said, I think that Julien's suggestion has merits. The fact that
> it can only handle up to 10 guests is not an issue, because the number
> of dom0less guests is lower than that in current scenarios. A similar
> idea would be to introduce an Emacs-like binding such as:
> 
>  Ctrl-A + (domid number)
> 
> to switch to a given domid.

FWIW I was thinking this as well.

 -George
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