Re: [Qemu-devel] [Qemu-ppc] [PATCH for-2.13 09/10] target/ppc: Don't bother with MSR_EP in cpu_ppc_set_papr()

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Apr 20, 2018 at 08:08:59AM +0200, Thomas Huth wrote:
> On 17.04.2018 09:17, David Gibson wrote:
> > cpu_ppc_set_papr() removes the EP and HV bits from the MSR mask.  While
> > removing the HV bit makes sense (a cpu in PAPR mode should never be
> > emulated in hypervisor mode), the EP bit is just bizarre.  Although it's
> > true that a papr mode guest shouldn't be able to change the exception
> > prefix, the MSR[EP] bit doesn't even exist on the cpus supported for PAPR
> > mode, so it's pointless to do anything with it here.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  target/ppc/translate_init.c | 9 ++++-----
> >  1 file changed, 4 insertions(+), 5 deletions(-)
> > 
> > diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
> > index 5e89901149..bb5559d799 100644
> > --- a/target/ppc/translate_init.c
> > +++ b/target/ppc/translate_init.c
> > @@ -8870,12 +8870,11 @@ void cpu_ppc_set_papr(PowerPCCPU *cpu, PPCVirtualHypervisor *vhyp)
> >  
> >      cpu->vhyp = vhyp;
> >  
> > -    /* PAPR always has exception vectors in RAM not ROM. To ensure this,
> > -     * MSR[IP] should never be set.
> > -     *
> > -     * We also disallow setting of MSR_HV
> > +    /*
> > +     * With a virtual hypervisor mode we never allow the CPU to go
> > +     * hypervisor mode itself
> >       */
> > -    env->msr_mask &= ~((1ull << MSR_EP) | MSR_HVB);
> > +    env->msr_mask &= ~MSR_HVB;
> >  
> >      /* Tell KVM that we're in PAPR mode */
> >      if (kvm_enabled()) {
> 
> Looks right.
> 
> Reviewed-by: Thomas Huth <thuth@redhat.com>

Turns out this one is pretty much independent of the rest of the
series, so I've merged it to ppc-for-2.13 already.


-- 
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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