Re: [PATCH v2 17/17] arm64: KVM: vgic-v3: Do not save ICH_AP0Rn_EL2 for GICv2 emulation

[Marc Zyngier <marc.zyngier@arm.com>]

On 03/03/16 19:21, Christoffer Dall wrote:
> On Wed, Feb 17, 2016 at 04:40:49PM +0000, Marc Zyngier wrote:
>> The GICv3 specification mandates that ICH_AP0Rn_EL2 are set to
>> zero when running guests that use the memory mapped registers.
>>
>> This is fine, as we initialize all ICH_AP0Rn_EL2 registers to
>> zero, and restore them on entry. But it also means that we
>> do not need to save these registers on exit. Profit!
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>>  arch/arm64/kvm/hyp/vgic-v3-sr.c | 19 +++++++++++--------
>>  1 file changed, 11 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c
>> index 5f12c57..c2f173d 100644
>> --- a/arch/arm64/kvm/hyp/vgic-v3-sr.c
>> +++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c
>> @@ -202,14 +202,17 @@ void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu)
>>  			__gic_v3_set_lr(0, i);
>>  		}
>>  
>> -		switch (nr_pri_bits) {
>> -		case 7:
>> -			cpu_if->vgic_ap0r[3] = read_gicreg(ICH_AP0R3_EL2);
>> -			cpu_if->vgic_ap0r[2] = read_gicreg(ICH_AP0R2_EL2);
>> -		case 6:
>> -			cpu_if->vgic_ap0r[1] = read_gicreg(ICH_AP0R1_EL2);
>> -		default:
>> -			cpu_if->vgic_ap0r[0] = read_gicreg(ICH_AP0R0_EL2);
>> +		/* ICH_AP0Rn is only valid for SRE==1 */
>> +		if (cpu_if->vgic_sre & ICC_SRE_EL1_SRE) {
>> +			switch (nr_pri_bits) {
>> +			case 7:
>> +				cpu_if->vgic_ap0r[3] = read_gicreg(ICH_AP0R3_EL2);
>> +				cpu_if->vgic_ap0r[2] = read_gicreg(ICH_AP0R2_EL2);
>> +			case 6:
>> +				cpu_if->vgic_ap0r[1] = read_gicreg(ICH_AP0R1_EL2);
>> +			default:
>> +				cpu_if->vgic_ap0r[0] = read_gicreg(ICH_AP0R0_EL2);
>> +			}
>>  		}
>>  
>>  		switch (nr_pri_bits) {
>> -- 
>> 2.1.4
>>
> 
> Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
> 

Looks like this patch, despite working fine on A57+GIC500, introduces a
regression on an internal build of the AEMv8 model. I'm chasing the
modelling guys in order to find out about it. In the meantime, I'll keep
it on the back-burner, just in case.

Thanks.

	M.
-- 
Jazz is not dead. It just smells funny...