[vbox-dev] Linux-4.12-rc1 and rc2 not working as vbox guest ?

[Frank Mehnert]

On Dienstag, 30. Mai 2017 09:14:31 CEST Hans de Goede wrote:
> On 29-05-17 17:28, Frank Mehnert wrote:
> > On Montag, 29. Mai 2017 16:58:28 CEST Frank Mehnert wrote:
> >> Hi Hans,
> >>
> >> On Montag, 29. Mai 2017 16:22:09 CEST Hans de Goede wrote:
> >>> [...]
> >>>
> >>> Ok, can you try install a 4.12 kernel, e.g.:
> >>>
> >>> https://koji.fedoraproject.org/koji/buildinfo?buildID=892258
> >>>
> >>> Download kernel-core... and kernel-modules... and then do
> >>> rpm -ivh kernel*.rpm
> >>> as root from a dir with the 2 downloaded files and boot
> >>> that on that skylake host (see below).
> >>
> >> thanks, your investigation was very helpful. Now I'm able to reproduce the
> >> problem with Fedora 25 with a 4.12-rc kernel on a Skylake host.
> > 
> > adding 'noxsave' to the kernel command line is a workaround.
> 
> Yes that works, thank you.

we did a bit more debugging. It really looks like this is a kernel bug. It
looks like the kernel wants to warn early about

  XSTATE_WARN_ON(paranoid_xstate_size != fpu_kernel_xstate_size);

(arch/x86/kernel/fpu/xstate.c:596)

but for some reason this warning becomes a panic and, even worse, no text
is displayed at all. The kernel is finally waiting in hlt. Same problem with
rc3 (using the 4.12.0-0.rc3.git1.1.fc27.x86_64 packages).

Adding 'noxsave' is a workaround because it prevents the kernel from using
xsave at all.

Again, this is not a VirtualBox bug although this panic will probably not
happen on real hardware.

Kind regards,

Frank
-- 
Dr.-Ing. Frank Mehnert | Software Development Director, VirtualBox
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