Re: [PATCH v2] KVM: s390: fix LPSWEY handling

[Sven Schnelle <svens@linux.ibm.com>]

Christian Borntraeger <borntraeger@linux.ibm.com> writes:

> Am 01.07.24 um 08:08 schrieb Sven Schnelle:
>> Christian Borntraeger <borntraeger@linux.ibm.com> writes:
>> 
>>> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
>>> index 1be19cc9d73c..1a49b89706f8 100644
>>> --- a/arch/s390/kvm/priv.c
>>> +++ b/arch/s390/kvm/priv.c
>>> @@ -797,6 +797,36 @@ static int handle_lpswe(struct kvm_vcpu *vcpu)
>>>   	return 0;
>>>   }
>>>   +static int handle_lpswey(struct kvm_vcpu *vcpu)
>>> +{
>>> +	psw_t new_psw;
>>> +	u64 addr;
>>> +	int rc;
>>> +	u8 ar;
>>> +
>>> +	vcpu->stat.instruction_lpswey++;
>>> +
>>> +	if (!test_kvm_facility(vcpu->kvm, 193))
>>> +		return kvm_s390_inject_program_int(vcpu, PGM_OPERATION);
>>> +
>>> +	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
>>> +		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
>>> +
>>> +	addr = kvm_s390_get_base_disp_siy(vcpu, &ar);
>>> +	if (addr & 7)
>>> +		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
>>> +
>>> +	rc = read_guest(vcpu, addr, ar, &new_psw, sizeof(new_psw));
>>> +	if (rc)
>>> +		return kvm_s390_inject_prog_cond(vcpu, rc);
>>> +
>>> +	vcpu->arch.sie_block->gpsw = new_psw;
>>> +	if (!is_valid_psw(&vcpu->arch.sie_block->gpsw))
>>> +		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
>> Shouldn't the gpsw get updated with new_psw after the check? POP
>> says "The operation
>> is suppressed on all addressing and protection exceptions."
>
> Only for exception of the instruction but not for the target PSW.
> POP says:
>
> The other PSW fields which are to be loaded by the
> instruction are not checked for validity before they are
> loaded. However, immediately after loading, a speci-
> fication exception is recognized, and a program inter-
> ruption occurs, when any of the following is true for
> the newly loaded PSW

Ok, sorry for the noise.