[virt-tools-list] [PATCH] virt-manager: console: add submenu for Alt-Sysrq key combos

[Martin Wilck]

On Tue, 2016-12-13 at 10:29 -0500, Cole Robinson wrote:
> On 12/13/2016 03:23 AM, Martin Wilck wrote:
> > On Mon, 2016-12-12 at 21:11 -0500, Cole Robinson wrote:

> > > Thanks for the patch, but I don't like the idea of an explicit
> > > sysrq
> > > list.
> > > It's linux guest specific, which isn't a stopper on its own,
> > > except
> > > even
> > > within linux distros it's not universal: at least fedora only
> > > enables
> > > a subset
> > > of the sysrq sequences by default, I assume that's the case for
> > > other
> > > distros
> > > as well. 
> > 
> > Hm, the same reasoning could be applied to key combos that are
> > already
> > present in the menu, such as ctlr-alt-backspace.
> 
> Notice I didn't defend the existing selection :) Those should be
> reworked too.
> 
> Even ctrl-alt-delete
> > doesn't necessarily have an effect.
> > 
> 
> ctrl-alt-delete may not work for some OS but it's absolutely
> essential for
> some windows versions, you can't even log in without it. So that's
> actually
> the element that most deserves to be in the list.

It surely does. I was just referring to your argument that Alt-SysRq
was "not universal".

[...]
> 
> Rethinking a bit, we could have an option like:
> 
> - Alt+Sysrq...
> 
> Which opens a small dialog that takes the extra Key. We could use
> that pattern
> for Ctrl+Alt as well to drop the backspace option and some or all of
> the 1-12
> options, I'd need to think about it more.

It's a good idea if the dialog really has to take a single key only.
Dialogs for key combos tend to be tricky to use.

> Just for reference, virtualbox exposes:
> 
> - Ctrl-alt-delete
> - Ctrl-alt-backspace
> - Ctrl-break
> - Insert
> - Printscreen
> - Alt-Printscreen

That looks windows-centric, as usual. I'd just hope that virt-manager
be a little more open-minded :-).

(Btw, I've also seen a number of vendor UIs for remote console access
and none of them exposed a reasonable way to enter alt-sysrq combos.
virt-manager could lead the way here :-)

> > > - A way for users to add their own permanent keycombos to the UI.
> > > This is
> > > discussed a bit in https://bugzilla.redhat.com/show_bug.cgi?id=10
> > > 1466
> > > 6 . If we
> > > go with the above 'manual' option, we could add a checkbox like
> > > 'Remember this
> > > key combo' that would permanently add it to the UI
> > 
> > That would be nice, but definitely outside my own scope, I just
> > need a
> > quick implementation of Alt-Sysrq.
> > 
> > Moreover, this is sort of over-engineered. The list of key combos
> > to be
> > supported is actually quite short; it must contain only combos that
> > are
> > a) important for some relevant guest OS and b) can't easily be
> > typed
> > the ordinary way in a VM console. Adding predefined sets of well-
> > known
> > key combos (perhaps depending on guest OS) would still make sense,
> > even
> > if a more generic approach was implemented. In my opinion, a useful
> > predefined set for Linux would have to include (at least some of)
> > the
> > Alt-Sysrq combos.
> 
> UI elements have a cost though, in testing, maintenance, possible
> user
> confusion leading to bug reports which take time/energy to triage,
> etc. Those
> factors have to be weighed against the value of the feature, such as
> how many
> people will use it, how critical it is for those users, and if there
> are
> workarounds (which there are, see below).

I understand. I was arguing for less engineering :-)

> > Lastly, I'd appreciate to have a solution for Alt-Sysrq quickly. My
> > patch could be a temporary solution while a more generic approach
> > is
> > under development. 
> 
> If you need a quick solution, there's 'virsh send-key' from the
> command line.

Yes, I know. I'd rather not start a discussion about the user-
friendlyness of that...

You are probably going to argue that people who know about alt-sysrq
can be expected to memorize "virsh send-key KEY_LEFTALT KEY_SYSRQ ..."
as well. You'd have a point. Maybe I'm getting old, I find that quite
hard to remember. Sure, I could write a shell script ... I was just
egoistically trying to make things a little smoother for people like
myself with this patch.

Thanks anyway for looking into this.

Martin

-- 
Dr. Martin Wilck <mwilck at suse.com>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)