Re: [PATCH 1/3] KVM: ARM64: Fix wrong use of the CPSR MODE mask

[Shannon Zhao <zhaoshenglong@huawei.com>]

On 2016/1/13 17:31, Marc Zyngier wrote:
> On 13/01/16 09:16, Shannon Zhao wrote:
>> From: Shannon Zhao <shannon.zhao@linaro.org>
>>
>> The values of CPSR MODE mask are different between aarch32 and aarch64.
>> It should use the right one according to the execution state.
>>
>> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
>> ---
>>  arch/arm64/include/asm/kvm_emulate.h | 8 ++++++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index 3066328..779a587 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -127,10 +127,14 @@ static inline unsigned long *vcpu_spsr(const struct kvm_vcpu *vcpu)
>>  
>>  static inline bool vcpu_mode_priv(const struct kvm_vcpu *vcpu)
>>  {
>> -	u32 mode = *vcpu_cpsr(vcpu) & PSR_MODE_MASK;
>> +	u32 mode;
>>  
>> -	if (vcpu_mode_is_32bit(vcpu))
>> +	if (vcpu_mode_is_32bit(vcpu)) {
>> +		mode = *vcpu_cpsr(vcpu) & COMPAT_PSR_MODE_MASK;
>>  		return mode > COMPAT_PSR_MODE_USR;
>> +	}
>> +
>> +	mode = *vcpu_cpsr(vcpu) & PSR_MODE_MASK;
>>  
>>  	return mode != PSR_MODE_EL0t;
>>  }
>>
> 
> Nice catch. At the moment, it will only affect perf's is_user_mode()
> with a 32bit guest (always reporting the guest as running in kernel
> mode), so that's not a big deal with mainline (but it clearly has a much
> bigger implication with the PMU support).
> 
> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
> 
Thanks, maybe this should backport to stable kernel. Sorry I forgot to
CC stable.

-- 
Shannon