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

[Thomas Huth <thuth@redhat.com>]

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>