Re: [Xen-devel] vnc=1 / pvgrub / close fb: backend at /local/domain/0/backend/vfb/xx/0

[Steven Haigh <netwiz@xxxxxxxxx>]

On 22/10/2014 8:59 PM, Samuel Thibault wrote:
> Ian Campbell, le Wed 22 Oct 2014 10:00:36 +0100, a écrit :
>> On Wed, 2014-10-22 at 08:24 +1100, Steven Haigh wrote:
>>> As a side note to this - if I use pygrub as a bootloader vs using
>>> pvgrub, then VNC works perfectly.
>>>
>>> So, what options exist to make pvgrub behave properly for booting with
>>> VNC enabled?
>>
>> ISTR (vaguely) that way back when the backends needed to be modified to
>> cope with kexec (which is effectively what pvgrub does) by not exiting
>> when the frontend disconnects, instead sticking around waiting for a new
>> frontend, this relates somehow to the "online" key in xenstore.
>>
>> Perhaps the pvfb backend never got that treatment, which would explain
>> #2? 
> 
> Probably, yes.
> 
>> That was ages ago (like 2005/6?)
> 
> 2007-2008 :)

I found lots of talk about this - mostly in Xen versions 3.x - although
I couldn't find anything recent. As such, I assumed it was fixed.

>> so it seems a bit unlikely you'd be the first to try this and notice.
> 
> Well, I guess there aren't so many people who use both pv-grub and a
> pvfb.

It seems like thats the case sadly. We have always pushed people towards
pv-grub for that extra bit of security - but a world of documentation
ignores the existence of pv-grub. As such, I doubt most people have even
stumbled across pv-grub.

I remember talk of pygrub being phased out - but I don't recall to what
extent or what timeframe that is.

>> I've no idea for #1 though.
> 
> I wonder too.
> 
>> Oh, is this with pvgrub 1 (the thing which ships with Xen) or pvgrub 2
>> (from the upstream grub project fairly recently)? Your logs hint towards
>> the former.
> 
> Yes, the logs definitely look like mini-os, thus pvgrub 1.

Yes, this is the Xen shipped pv-grub. I haven't found any mention of
pvgrub 2 before - any links for that? I assume it can just be built and
called from within the DomU config?

-- 
Steven Haigh

Email: netwiz@xxxxxxxxx
Web: http://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897
Fax: (03) 8338 0299

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