From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: Regression due to
 d9581c7dcac15c02ad4d47c60c60f4d8f197db55 en/fb: allow xenfb initialization
 for hvm guest
Date: Tue, 3 Mar 2015 10:20:56 -0500
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To: Ian Campbell <ian.campbell@citrix.com>
Cc: xen-devel@lists.xensource.com, David Vrabel <david.vrabel@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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> > > I am afraid that Xend is still widespread enough that we need some way to
> > > deal with it.
> > > 
> > > The #idef hackery - while not a nice way can make this work.
> > > 
> > > Or we can add this in an header/function as a quirk.
> > > 
> > > boolean xen_pvfb_dont_init_quirk(void)
> > > {
> > > #ifdef CONFIG_X86
> > 
> > I would be OK with having such a quirk without the ifdef (no xend has
> > been known to work on ARM anyway).
> >  
> > 
> > > 	if (xen_running_on_version_or_later(4, 5) && xen_hvm_domain())
> > 
> > Shouldn't this be xen_running_on_version_or_earlier(4, 4)?
> > Xend has been removed in 4.5.
> 
> This all sounds pretty gross, but if it is the way folks want to go,
> shouldn't it try and determine that it is running on xend somehow
> instead of guessing based on version number? 4.4 had xl in it too for
> instance...

Right, so the secondary check would be to see if there is something
extra that Xend puts in the XenStore. And it looks to always
put 'protocol' in every device:

xm:
0 = ""
 protocol = "x86_32-abi"
 state = "1"
 backend-id = "0"
 backend = "/local/domain/0/backend/vfb/7/0"

While xl:
vfb = ""
 0 = ""
  backend = "/local/domain/0/backend/vfb/1/0"
  backend-id = "0"
  state = "1"