Re: [PATCH v2 11/17] kvm: arm64: Configure VTCR per VM

[Suzuki K Poulose]

On 03/05/18 15:39, James Morse wrote:
> Hi Suzuki,
>
> On 27/03/18 14:15, Suzuki K Poulose wrote:
> > We set VTCR_EL2 very early during the stage2 init and don't
> > touch it ever. This is fine as we had a fixed IPA size. This
> > patch changes the behavior to set the VTCR for a given VM,
> > depending on its stage2 table. The common configuration for
> > VTCR is still performed during the early init as we have to
> > retain the hardware access flag update bits (VTCR_EL2_HA)
> > per CPU (as they are only set for the CPUs which are capabile).
> > The bits defining the number of levels in the page table (SL0)
> > and and the size of the Input address to the translation (T0SZ)
> > are programmed for each VM upon entry to the guest.
>
>
> > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > index 596f8e4..9f3c8b8 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -392,10 +392,12 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
> >   
> >   static inline void __cpu_init_stage2(void)
> >   {
> > -	u32 parange = kvm_call_hyp(__init_stage2_translation);
> > +	u32 ps;
> >   
> > -	WARN_ONCE(parange < 40,
> > -		  "PARange is %d bits, unsupported configuration!", parange);
> > +	kvm_call_hyp(__init_stage2_translation);
> > +	ps = id_aa64mmfr0_parange_to_phys_shift(read_sysreg(id_aa64mmfr0_el1));
>
> Doesn't id_aa64mmfr0_parange_to_phys_shift() expect you do to the mask and shift
> for it? This will always hit the default case.

Good catch ! The error case was not hit on the system I tested, as it was
indeed having 48bit PA. I should have done more testing with Juno where it
is 40bit PA (which doesn't really allow different phys-shift ranges).

I will change the helper to extract the parange and the convert it.
Also, rename it to :

id_aa64mmfr0_phys_shift()

Cheers
Suzuki

> > +	WARN_ONCE(ps < 40,
> > +		  "PARange is %d bits, unsupported configuration!", ps);
> >   }
>
>
>
> Thanks,
>
> James