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

From: "Jan Beulich" <JBeulich@suse.com>
To: Julien Grall <julien.grall@arm.com>
Cc: Tim Deegan <tim@xen.org>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Wei Liu <wei.liu2@citrix.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Stefano Stabellini <stefanos@xilinx.com>,
	Ian Jackson <Ian.Jackson@eu.citrix.com>,
	xen-devel@lists.xen.org,
	"andrii_anisov@epam.com" <andrii_anisov@epam.com>,
	nd@arm.com
Subject: Re: [PATCH v2 20/21] xen: support console_switching between Dom0 and DomUs on ARM
Date: Thu, 19 Jul 2018 00:10:42 -0600	[thread overview]
Message-ID: <5B502B6202000078001D5A90@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <e4e16cba-2545-1b4e-e15c-ac10c1a2b8a5@arm.com>

>>> On 18.07.18 at 18:59, <julien.grall@arm.com> wrote:
> On 18/07/18 08:12, 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.
> 
> That what I had in mind. I agree that this solution would not scale to 
> Dom10 and beyond. But that ring solution is not going to be any better.
> 
> Let's imagine you want to switch between domain 9 and 8. You would need 
> to type CTRL-AAA N time before reaching the right console. N been the 
> number of domain you have using the console.
> 
> It feels like, you want to provide a key for selecting the console (e.g 
> 'c') and then type the domain ID you want to access. Can you read 
> another key when in the keyhandler?

Well, as always - everything can be made work which is at least
theoretically possible. We don't have any example of this so far,
but I don't think it would be overly complicated.

Jan

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