Re: [PATCH v2 24/42] KVM: s390: protvirt: STSI handling

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 18.02.20 09:35, David Hildenbrand wrote:
> On 14.02.20 23:26, Christian Borntraeger wrote:
>> From: Janosch Frank <frankja@linux.ibm.com>
>>
>> Save response to sidad and disable address checking for protected
>> guests.
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> Reviewed-by: Thomas Huth <thuth@redhat.com>
>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>> [borntraeger@de.ibm.com: patch merging, splitting, fixing]
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> ---
>>  arch/s390/kvm/priv.c | 11 ++++++++---
>>  1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
>> index ed52ffa8d5d4..b2de7dc5f58d 100644
>> --- a/arch/s390/kvm/priv.c
>> +++ b/arch/s390/kvm/priv.c
>> @@ -872,7 +872,7 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
>>  
>>  	operand2 = kvm_s390_get_base_disp_s(vcpu, &ar);
>>  
>> -	if (operand2 & 0xfff)
>> +	if (!kvm_s390_pv_is_protected(vcpu->kvm) && (operand2 & 0xfff))
>>  		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
> 
> Why is that needed? I'd assume the hardware handles this for us and this
> case can never happen for PV? (IOW, change is not necessary)

Hardware is handling this for us AND we are not allowed to inject a specification
exception. The ultravisor guards the program checks that we are allowed to inject.

> 
>>  
>>  	switch (fc) {
>> @@ -893,8 +893,13 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
>>  		handle_stsi_3_2_2(vcpu, (void *) mem);
>>  		break;
>>  	}
>> -
>> -	rc = write_guest(vcpu, operand2, ar, (void *)mem, PAGE_SIZE);
>> +	if (kvm_s390_pv_is_protected(vcpu->kvm)) {
>> +		memcpy((void *)sida_origin(vcpu->arch.sie_block), (void *)mem,
>> +		       PAGE_SIZE);
>> +		rc = 0;
>> +	} else {
>> +		rc = write_guest(vcpu, operand2, ar, (void *)mem, PAGE_SIZE);
>> +	}
>>  	if (rc) {
>>  		rc = kvm_s390_inject_prog_cond(vcpu, rc);
>>  		goto out;
>>
> 
> I'd pull the interrupt injection into the else case, makes things clearer.

Well, no. Thhe else case could set rc to 0.

> 
> What about user_stsi? Will that still work? (I assume user space will
> write to the sida and it should work just fine)

will still work. 
> 
> (I assume races regarding kvm_s390_pv_is_protected() will be dealt with
> in your next series)
> 
> In general, looks good to me.
>