Re: Utility of PV on non-obsolete hardware

[tg%gmplib.org@localhost (Torbjörn Granlund)]

Greg Troxel <gdt%lexort.com@localhost> writes:

  A good start would be someone who is running PVHVM or HVM mode sending a
  note to this list with:

    which netbsd and xen versions support what they are doing, or which
    versions they know support it

    what goes in the config file that's different from the (pv) examples

  We don't need anything fancy.  Somebody who understands who takes 5
  minutes to send the above message, and somebody willing to edit the wiki
  for 15 minutes is all we are talking about.

I've been running NetBSD under PV under countless Xen versions (formerly
under a NetBSD Dom0 and later under Gentoo GNU/Linux Dom0).

I've only recently ran NetBSD HVM, and then only under Xen 4.10.2,
4.10.3, 4.11.1, and 4.12.0.

Sample config file:

================================================================
type = 'hvm'
memory = 1024
vcpus = 1
name = "nbsd64v72hvm"
vif  = ['mac=00:16:3e:64:72:5f, model=virtio-net, bridge=br0']
disk = ['phy:/dev/vgb/netbsd-64-72hvm,xvda,w',
        'file:/var/tmp/NetBSD-7.2-amd64.iso,hdc:cdrom,r'
        ]
boot = 'cd'
vnc = 0
sdl = 0
acpi = 1
apic = 1
pae = 1
usb=1
serial='pty'
================================================================

Notes:

I do nothing fancy for the install, but make sure to install the NetBSD
boot code.  For the sake of alignment, I edit the mbr to start the first
(and only) NetBSD partition at 1MB.

The "boot = 'cd'" configuration might warrant some comment.  That means
"attempt bootfrom harddrive first, and if that is unsuccessful, boot
from CD.  This only works if the disk provided (here
/dev/vgb/netbsd-64-72hvm) is essentially blank.  A more resilient option
is to pass "boot = 'd'" for install, then change that to 'c'.  (Or
perhaps remove he cd config and boot= altogether.)



I urge you to make clear that HVM is typically faster than PV on any
current or semi-current hardware, except for very I/O intensive guests.
For me, HVM is WAY faster, and my buidling tasks do perform a fair bit
of I/O.


-- 
Torbjörn
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