Re: annual howto rampage

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Jul 12, 2024 at 10:31:50AM -0400, Greg Troxel wrote:
> Manuel Bouyer <bouyer%antioche.eu.org@localhost> writes:
> 
> > Well, AFAIK PVH uses the HVM hardware extention to virtualise the pagetables.
> > I don't have x86 host without VT-X anymore so I can't really test this.
> 
> ok.  the text now reflects that "it is theoretically required but i386
> pvh/pvshim seems ok anyway"
> 
> >> Regarding your tests:
> >> 
> >>   I don't see PVHVM mode.  Is that because it doesn't work, or because
> >>   you just don't, or ?
> >
> > HVM tests are really PVHVM, as GENERIC includes the PV drivers and there's no
> > real way to disable the PV drivers at the xl level (AFAIK)
> 
> ah, makes senes.
> 
> How does the dom0 withdraw the non-pv disk in pvhvm mode, and how does
> it know to do so?

in sys/arch/xen/xen/hypervisor.c see XEN_MAGIC_IOPORT and XMI_* enum

Basically, when the hypervisorbus is attached, it sends a command to
the qemu process asking to stop emulating the disk and nic devices.
hypervisorbus is attached before PCI and ISA devices

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--