Re: Urgent: NetBSD domUs will not start after Xen kernel update

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

On Mon, Oct 23, 2017 at 08:15:46PM +0100, David Brownlee wrote:
> On 23 October 2017 at 17:33, Manuel Bouyer <bouyer%antioche.eu.org@localhost> wrote:
> > On Mon, Oct 23, 2017 at 05:14:10PM +0100, Stephen Borrill wrote:
> >> Thanks for your quick reply. I can confirm that the following command gets
> >> VMs booting again:
> >> /opt/xensource/libexec/xen-cmdline --set-xen pv-linear-pt=true
> >>
> >> i.e.
> >> # xl info | grep commandline
> >> xen_commandline        : dom0_mem=752M,max:752M watchdog ucode=scan dom0_max_vcpus=4 crashkernel=128M@256M console=vga vga=mode-0x0311 pv-linear-pt=true
> >>
> >> However, while this is a useful workaround, it's not great going forward as
> >> the command line may be modified when other hotfixes or upgrades happen (or,
> >> of course, may not be under your administrative control). What's the roadmap
> >> for fixing this in the NetBSD kernel?
> >
> > The x86 pmap makes heavy use of linear mappings, so it's not going to be
> > "fixed" anytime soon (actually I consider it's a bug in Xen that it is
> > disabled by default).
> 
> How complicated would it be to detect this case in a NetBSD DOM0 and
> panic with an appropriate message, so users know what to adjust?

I don't think it's much or a problem for dom0, because the xen kernels
from pkgsrc have linear mappings on by default.
The problem is more with NetBSD domUs on linux dom0.

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