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

Martin Wilck mwilck at suse.com
Tue Dec 13 08:23:37 UTC 2016

On Mon, 2016-12-12 at 21:11 -0500, Cole Robinson wrote:
> On 12/06/2016 02:40 PM, Martin Wilck wrote:
> > This patch adds a submenu with Alt-SysRq key combinations to the
> > "Send Key" menu of the virt-manager console. As this is useful
> > mostly
> > for Linux guests, I added the Linux key "translations" to the menu.
> > 
> > Feedback is welcome.
> > 
> 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. Even ctrl-alt-delete
doesn't necessarily have an effect.

> In this case the UI would lead people down the wrong path and I can
> imagine fielding bug requests about why a virt-manager menu entry
> didn't do
> what it claims to do (like kill-all-tasks)

Such reports would be quite easily dismissed, in particular because the
kernel prints a message on the console telling the user that the sysrq
combo is disabled.

I agree that my proposed labeling of the options with strings like
"kill-all-tasks" isn't optimal. Simply labeling it "Ctrl-Alt-t" would
be less misleading, because that wouldn't suggest a specific effect.

I'd be happy to resend my patch with those labels changed. I'd also
agree to add functionality make the presence of this menu depend on a
(global) configuration option that the user must enable explicitly. 

> I'd rather see this solved with two bits:
> - A menu option to pass a manual keycombo to the guest. So it would
> allow the
> user to press alt+sysrq+s individually, then click a 'send' button or
> similar.
> Slow, but flexible

IMO that would likely cause user frustration.

> - 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=101466
> 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.

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. The Red Hat bugzilla you mentioned has been open for
3 years ... is there hope for a full solution to be implemented anytime


> Thanks,
> Cole

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)

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