Re: [Xen-devel] [PATCH v4] add support for libvirt-like channels

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-09-10 at 14:45 +0100, Dave Scott wrote:

> > I'm trying to get a feel for how worried I should be about the potential
> > for regressing existing guests with this change.
> 
> I believe the âtypeâ frontend key has always been read/only (at least within 
> recent memory):
> 
> 28d386fc        (Ian Jackson    2013-06-25 11:24:22 +0100       3321)    
> flexarray_append(ro_front, "type");
> ffa165bb        (Ian Campbell   2012-03-01 12:26:14 +0000       3322)    if 
> (console->consback == LIBXL__CONSOLE_BACKEND_XENNSOLED)
> 28d386fc        (Ian Jackson    2013-06-25 11:24:22 +0100       3323)        
> flexarray_append(ro_front, "xenconsoled");
> 5588033d        (Ian Campbell   2010-10-05 17:51:28 +0100       3324)    else
> 28d386fc        (Ian Jackson    2013-06-25 11:24:22 +0100       3325)        
> flexarray_append(ro_front, "ioemuâ);

Ah, looks like it was since XSA-57, which was about unduly lose xenstore
permissions.

> As a sanity check I just fired up a Fedora 20 guest with a single (primary) 
> console. In xenstore the key is read-only as expected:
> 
> $ sudo xenstore-ls /local/domain/3/console -p
> backend = "/local/domain/0/backend/console/3/0"  . . . . . .  (n0,r3)
> backend-id = "0" . . . . . . . . . . . . . . . . . . . . . .  (n3,r0)
> limit = "1048576"  . . . . . . . . . . . . . . . . . . . . .  (n0,r3)
> type = "xenconsoled" . . . . . . . . . . . . . . . . . . . .  (n0,r3)
> output = "pty" . . . . . . . . . . . . . . . . . . . . . . .  (n0,r3)
> tty = "/dev/pts/1" . . . . . . . . . . . . . . . . . . . . .  (n0,r3)
> port = "2" . . . . . . . . . . . . . . . . . . . . . . . . .  (n0,r3)
> ring-ref = "1044479" . . . . . . . . . . . . . . . . . . . .  (n0,r3)
> vnc-listen = "0.0.0.0" . . . . . . . . . . . . . . . . . . .  (n0,r3)
> vnc-port = "5900"  . . . . . . . . . . . . . . . . . . . . .  (n0,r3)
> 
> And when I attached âscreenâ to â/dev/pts/1â I found a getty.
> 
> I also had a quick look at what pre-libxl xapi does â it seems not to create 
> a âtypeâ key at all. Primary consoles seem to work ok.
> 
> I did a quick rebase and retest of these patches. Iâm personally fairly 
> confident that nothing bad will happen but Iâm a little biased ;-)
> 
> Let me know if I should resend. If you want to take a look theyâre hosted in 
> this branch:
> 
>   git pull git://github.com/djs55/xen add-channels10

I think you should probably wait for IanJ's input, since he had some
thoughts last time wrt the protocol docs etc.

Ian

> 
> Cheers,
> Dave



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