Re: NetBSD 9.0 RC1 amd64 not working on VirtualBox 6.1.0

[Bodie <bodie%bodie.cz@localhost>]

On 12.12.2019 17:38, Maxime Villard wrote:
> Le 12/12/2019 à 16:34, Valery Ushakov a écrit :
> > On Thu, Dec 12, 2019 at 06:47:50 +0100, Bodie wrote:
> >
> > > On 11.12.2019 23:32, Valery Ushakov wrote:
> > > > On Wed, Dec 11, 2019 at 23:15:38 +0100, Bodie wrote:
> > > >
> > > > > FYI https://www.virtualbox.org/ticket/19146
> > > > >
> > > > > Not possible to boot installer of NetBSD 9.0RC1. cc me as I am not
> > > > > subscribed to list.
> > > >
> > > > CPUID values are ... = guest (host):
> > > >
> > > > IBRS_IBPB - IA32_SPEC_CTRL.IBRS and IA32_PRED_CMD.IBPB  = 0 (1)
> > > > STIBP - Supports IA32_SPEC_CTRL.STIBP                   = 0 (1)
> > > > SSBD - Supports IA32_SPEC_CTRL.SSBD                     = 0 (1)
> > > >
> > > > so the NetBSD guest is told the cpu doesn't support IA32_SPEC_CTRL
> > > > (0x48),
> > > > but still the guest tries to read it:
> > >
> > > NetBSD 8.1 STABLE amd64 on same configuration with same values boots
> > > just fine and works.
> >
> > Right, b/c NetBSD 8 doesn't read that nonexistent MSR.
> >
> >
> > > > 00:00:11.518912 IEM: rdmsr(0x48) -> #GP(0)
> > > > 00:00:11.518920 Changing the VM state from 'RUNNING' to
> > > > 'GURU_MEDITATION'
> >
> > 00:00:11.520158 CPUM0: 0008:ffffffff8022714b 0f 32                   
> > rdmsr
> >
> > This is mitigation_v2_apply_cpu(), V2_MITIGATION_INTEL_ENHANCED_IBRS
> > case it seems, so either the kernel misdetects the mitigation variant
> > to use, or vbox doesnt' scrub host capabilities enough.  Someone with
> > the clue should look at the VBox.log (it has the cpuinfo dump).
> >
> > -uwe
>
> The CPU has
>
> 	CPUID.IBRS = 1
> 	CPUID.STIBP = 1
> 	ARCH_CAP.IBRS_ALL = 1
>
> VirtualBox only clears the CPUID:
>
> 	CPUID.IBRS = 0
> 	CPUID.STIBP = 0
> 	ARCH_CAP.IBRS_ALL = 1
>
> NetBSD sees ARCH_CAP.IBRS_ALL == 1, and tries to use the SPEC_CTRL MSR, 
> which
> faults.
>
> Technically, NetBSD is not wrong, because you cannot have 
> ARCH_CAP.IBRS_ALL set
> to one and CPUID.IBRS/STIBP set to zero. Still, I will add a check on 
> the
> CPUIDs.

Once there will be some daily build to check I can do that of course.

> Meanwhile VirtualBox should be fixed not to report ARCH_CAP.IBRS_ALL, 
> because
> this is technically incorrect.

yeah it may take a while I fear
> Maxime