Re: XEN3_DOM0 rationalization

[John Nemeth <jnemeth%cue.bc.ca@localhost>]

On Mar 7, 14:31, Greg Troxel wrote:
} John Nemeth <jnemeth%cue.bc.ca@localhost> writes:
} > On Mar 7, 13:47, Greg Troxel wrote:
} > } 
} > } Right now I think people need to read the HOWTO to figure out how to set
} > } up Xen on NetBSD.  It's getting even more complicated with PVHVM and PVH
} >
} >      Pretty much all complex software has some kind of learning
} > curve.  I really don't view this as a negative.  Would you expect
} > to be able to setup Asterisk, Samba, any other virtual environment,
} > etc.  without doing some reading?
} 
} Agreed.   I just meant that "people will be led astray by the kernel
} name" is to me not a compelling argument.

     Ah, okay.

} >      PVHVM and PVH are in their infancy and can be ignored by most
} > people for now.  I certainly wouldn't include them in the HOWTO at
} > this point,  Also, last I knew we hadn't done much at all with PVH.
} > The difference is PVHVM is domU running in HVM mode, but with access
} > to PV devices (much more efficient since device emulation isn't
} > needed).  Whereas PVH is for dom0 so that it runs in an HVM like
} > mode.
} 
} I guess we can argue about HOWTO vs WHATIS, but I think if it exists at
} all in the Xen world it should be described whether or not it works on
} NetBSD, how to do it if so, and advice not to use it if that's the
} consensus.

     I am going to strongly disagree with this statement.  The
NetBSD HOWTO is exactly that, a HOWTO about using Xen with NetBSD.
There is plenty of generic Xen documentation.

} I thought PVH was also for domU, to be sort of HVM with PV drivers, but
} so that the dom0 didn't need to run a (terrifying security wise) qemu.

     No, PVH is strictly for dom0.  What you're describing is PVHVM.
There are also stub domains, which is where qemu is run in its own
domU with just the privileges needed.  Unfortunately whenever I've
talked to Xen developers, I've been told that stub domains are
highly Linux-centric.

} HVM is reported to work badly on some Linux dom0 setups in terms of disk
} performance, to the point that it is unusable.  And our PV in current

     Ouch!  Of course, they are likely to tell you to use PVHVM.
This is easier said than done.  I've tried to get the Windows PV
drivers to work with modern Windows and didn't have any luck.

} runs into trouble in current with dom0s that use the version of grant
} tables we don't.  Yes, that's fuzzy which is why it isn't quite in the
} HOWTO.

     Our usage of grant tables seems to be a bit of a mess right
now.  This is going to need somebody with some knowledge of the
subject and time to dig into it.

}-- End of excerpt from Greg Troxel