Re: [PATCH] KVM: s390: fix cc for successful PQAP

[Anthony Krowiak <akrowiak@linux.ibm.com>]

On 12/1/23 1:16 PM, Eric Farman wrote:
> The various errors that are possible when processing a PQAP
> instruction (the absence of a driver hook, an error FROM that
> hook), all correctly set the PSW condition code to 3. But if
> that processing works successfully, CC0 needs to be set to
> convey that everything was fine.
>
> Fix the check so that the guest can examine the condition code
> to determine whether GPR1 has meaningful data.
>
> Fixes: e5282de93105 ("s390: ap: kvm: add PQAP interception for AQIC")
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> ---
>   arch/s390/kvm/priv.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 621a17fd1a1b..f875a404a0a0 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -676,8 +676,12 @@ static int handle_pqap(struct kvm_vcpu *vcpu)
>   	if (vcpu->kvm->arch.crypto.pqap_hook) {
>   		pqap_hook = *vcpu->kvm->arch.crypto.pqap_hook;
>   		ret = pqap_hook(vcpu);
> -		if (!ret && vcpu->run->s.regs.gprs[1] & 0x00ff0000)
> -			kvm_s390_set_psw_cc(vcpu, 3);
> +		if (!ret) {
> +			if (vcpu->run->s.regs.gprs[1] & 0x00ff0000)
> +				kvm_s390_set_psw_cc(vcpu, 3);
> +			else
> +				kvm_s390_set_psw_cc(vcpu, 0);
> +		}


The cc is not set if pqap_hook returns a non-zero rc; however, this 
point may be moot given the only non-zero rc is -EOPNOTSUPP. I'm a bit 
foggy on what happens when non-zero return codes are passed up the stack.


>   		up_read(&vcpu->kvm->arch.crypto.pqap_hook_rwsem);
>   		return ret;
>   	}