[PATCH v3 30/33] KVM: PPC: Book3S HV: Allow HV module to load without hypervisor mode

[David Gibson]

On Thu, Oct 04, 2018 at 01:03:21PM +1000, Paul Mackerras wrote:
> On Wed, Oct 03, 2018 at 04:15:15PM +1000, David Gibson wrote:
> > On Tue, Oct 02, 2018 at 09:31:29PM +1000, Paul Mackerras wrote:
> > > With this, the KVM-HV module can be loaded in a guest running under
> > > KVM-HV, and if the hypervisor supports nested virtualization, this
> > > guest can now act as a nested hypervisor and run nested guests.
> > > 
> > > This also adds some checks to inform userspace that HPT guests are not
> > > supported by nested hypervisors, and to prevent userspace from
> > > configuring a guest to use HPT mode.
> > > 
> > > Signed-off-by: Paul Mackerras <paulus at ozlabs.org>
> > > ---
> > >  arch/powerpc/kvm/book3s_hv.c | 20 ++++++++++++++++----
> > >  1 file changed, 16 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> > > index f630e91..196bff1 100644
> > > --- a/arch/powerpc/kvm/book3s_hv.c
> > > +++ b/arch/powerpc/kvm/book3s_hv.c
> > > @@ -4237,6 +4237,10 @@ static int kvm_vm_ioctl_get_smmu_info_hv(struct kvm *kvm,
> > >  {
> > >  	struct kvm_ppc_one_seg_page_size *sps;
> > >  
> > > +	/* If we're a nested hypervisor, we only support radix guests */
> > > +	if (kvmhv_on_pseries())
> > > +		return -EINVAL;
> > > +
> > >  	/*
> > >  	 * POWER7, POWER8 and POWER9 all support 32 storage keys for data.
> > >  	 * POWER7 doesn't support keys for instruction accesses,
> > > @@ -4822,11 +4826,15 @@ static int kvmppc_core_emulate_mfspr_hv(struct kvm_vcpu *vcpu, int sprn,
> > >  
> > >  static int kvmppc_core_check_processor_compat_hv(void)
> > >  {
> > > -	if (!cpu_has_feature(CPU_FTR_HVMODE) ||
> > > -	    !cpu_has_feature(CPU_FTR_ARCH_206))
> > > -		return -EIO;
> > > +	if (cpu_has_feature(CPU_FTR_HVMODE) &&
> > > +	    cpu_has_feature(CPU_FTR_ARCH_206))
> > > +		return 0;
> > >  
> > > -	return 0;
> > > +	/* Can run as nested hypervisor on POWER9 in radix mode. */
> > > +	if (cpu_has_feature(CPU_FTR_ARCH_300) && radix_enabled())
> > 
> > Shouldn't we probe the parent hypervisor for ability to support nested
> > guests before we say "yes" here?
> 
> Well, we do check that the parent hypervisor can support nested
> hypervisors, it's just done later on.  And to match nitpick with
> nitpick, this is a function evaluating _processor_ compatibility, and
> a POWER9 processor in radix mode does have everything necessary to
> support nested hypervisors -- if the parent hypervisor doesn't support
> nested hypervisors, that's not a deficiency in the processor.

Fair enough.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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