Re: [PATCH v3 1/1] KVM: s390: vsie: clarifications on setting the APCB

[Pierre Morel <pmorel@linux.ibm.com>]

On 2/16/23 14:41, Janosch Frank wrote:
> On 2/14/23 13:28, Pierre Morel wrote:
>> The APCB is part of the CRYCB.
>> The calculation of the APCB origin can be done by adding
>> the APCB offset to the CRYCB origin.
>>
>> Current code makes confusing transformations, converting
>> the CRYCB origin to a pointer to calculate the APCB origin.
>>
>> Let's make things simpler and keep the CRYCB origin to make
>> these calculations.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> 
> LGTM:
> Acked-by: Janosch Frank <frankja@linux.ibm.com>

Thanks,
Pierre

> 
>> ---
>>   arch/s390/kvm/vsie.c | 50 +++++++++++++++++++++++++-------------------
>>   1 file changed, 29 insertions(+), 21 deletions(-)
>>
>> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
>> index b6a0219e470a..8d6b765abf29 100644
>> --- a/arch/s390/kvm/vsie.c
>> +++ b/arch/s390/kvm/vsie.c
>> @@ -138,11 +138,15 @@ static int prepare_cpuflags(struct kvm_vcpu 
>> *vcpu, struct vsie_page *vsie_page)
>>   }
>>   /* Copy to APCB FORMAT1 from APCB FORMAT0 */
>>   static int setup_apcb10(struct kvm_vcpu *vcpu, struct kvm_s390_apcb1 
>> *apcb_s,
>> -            unsigned long apcb_o, struct kvm_s390_apcb1 *apcb_h)
>> +            unsigned long crycb_gpa, struct kvm_s390_apcb1 *apcb_h)
>>   {
>>       struct kvm_s390_apcb0 tmp;
>> +    unsigned long apcb_gpa;
>> -    if (read_guest_real(vcpu, apcb_o, &tmp, sizeof(struct 
>> kvm_s390_apcb0)))
>> +    apcb_gpa = crycb_gpa + offsetof(struct kvm_s390_crypto_cb, apcb0);
>> +
>> +    if (read_guest_real(vcpu, apcb_gpa, &tmp,
>> +                sizeof(struct kvm_s390_apcb0)))
>>           return -EFAULT;
>>       apcb_s->apm[0] = apcb_h->apm[0] & tmp.apm[0];
>> @@ -157,15 +161,19 @@ static int setup_apcb10(struct kvm_vcpu *vcpu, 
>> struct kvm_s390_apcb1 *apcb_s,
>>    * setup_apcb00 - Copy to APCB FORMAT0 from APCB FORMAT0
>>    * @vcpu: pointer to the virtual CPU
>>    * @apcb_s: pointer to start of apcb in the shadow crycb
>> - * @apcb_o: pointer to start of original apcb in the guest2
>> + * @crycb_gpa: guest physical address to start of original guest crycb
>>    * @apcb_h: pointer to start of apcb in the guest1
>>    *
>>    * Returns 0 and -EFAULT on error reading guest apcb
>>    */
>>   static int setup_apcb00(struct kvm_vcpu *vcpu, unsigned long *apcb_s,
>> -            unsigned long apcb_o, unsigned long *apcb_h)
>> +            unsigned long crycb_gpa, unsigned long *apcb_h)
>>   {
>> -    if (read_guest_real(vcpu, apcb_o, apcb_s,
>> +    unsigned long apcb_gpa;
>> +
>> +    apcb_gpa = crycb_gpa + offsetof(struct kvm_s390_crypto_cb, apcb0);
>> +
>> +    if (read_guest_real(vcpu, apcb_gpa, apcb_s,
>>                   sizeof(struct kvm_s390_apcb0)))
>>           return -EFAULT;
>> @@ -178,16 +186,20 @@ static int setup_apcb00(struct kvm_vcpu *vcpu, 
>> unsigned long *apcb_s,
>>    * setup_apcb11 - Copy the FORMAT1 APCB from the guest to the shadow 
>> CRYCB
>>    * @vcpu: pointer to the virtual CPU
>>    * @apcb_s: pointer to start of apcb in the shadow crycb
>> - * @apcb_o: pointer to start of original guest apcb
>> + * @crycb_gpa: guest physical address to start of original guest crycb
>>    * @apcb_h: pointer to start of apcb in the host
>>    *
>>    * Returns 0 and -EFAULT on error reading guest apcb
>>    */
>>   static int setup_apcb11(struct kvm_vcpu *vcpu, unsigned long *apcb_s,
>> -            unsigned long apcb_o,
>> +            unsigned long crycb_gpa,
>>               unsigned long *apcb_h)
>>   {
>> -    if (read_guest_real(vcpu, apcb_o, apcb_s,
>> +    unsigned long apcb_gpa;
>> +
>> +    apcb_gpa = crycb_gpa + offsetof(struct kvm_s390_crypto_cb, apcb1);
>> +
>> +    if (read_guest_real(vcpu, apcb_gpa, apcb_s,
>>                   sizeof(struct kvm_s390_apcb1)))
>>           return -EFAULT;
>> @@ -200,7 +212,7 @@ static int setup_apcb11(struct kvm_vcpu *vcpu, 
>> unsigned long *apcb_s,
>>    * setup_apcb - Create a shadow copy of the apcb.
>>    * @vcpu: pointer to the virtual CPU
>>    * @crycb_s: pointer to shadow crycb
>> - * @crycb_o: pointer to original guest crycb
>> + * @crycb_gpa: guest physical address of original guest crycb
>>    * @crycb_h: pointer to the host crycb
>>    * @fmt_o: format of the original guest crycb.
>>    * @fmt_h: format of the host crycb.
>> @@ -211,50 +223,46 @@ static int setup_apcb11(struct kvm_vcpu *vcpu, 
>> unsigned long *apcb_s,
>>    * Return 0 or an error number if the guest and host crycb are 
>> incompatible.
>>    */
>>   static int setup_apcb(struct kvm_vcpu *vcpu, struct 
>> kvm_s390_crypto_cb *crycb_s,
>> -           const u32 crycb_o,
>> +           const u32 crycb_gpa,
>>              struct kvm_s390_crypto_cb *crycb_h,
>>              int fmt_o, int fmt_h)
>>   {
>> -    struct kvm_s390_crypto_cb *crycb;
>> -
>> -    crycb = (struct kvm_s390_crypto_cb *) (unsigned long)crycb_o;
>> -
>>       switch (fmt_o) {
>>       case CRYCB_FORMAT2:
>> -        if ((crycb_o & PAGE_MASK) != ((crycb_o + 256) & PAGE_MASK))
>> +        if ((crycb_gpa & PAGE_MASK) != ((crycb_gpa + 256) & PAGE_MASK))
>>               return -EACCES;
>>           if (fmt_h != CRYCB_FORMAT2)
>>               return -EINVAL;
>>           return setup_apcb11(vcpu, (unsigned long *)&crycb_s->apcb1,
>> -                    (unsigned long) &crycb->apcb1,
>> +                    crycb_gpa,
>>                       (unsigned long *)&crycb_h->apcb1);
>>       case CRYCB_FORMAT1:
>>           switch (fmt_h) {
>>           case CRYCB_FORMAT2:
>>               return setup_apcb10(vcpu, &crycb_s->apcb1,
>> -                        (unsigned long) &crycb->apcb0,
>> +                        crycb_gpa,
>>                           &crycb_h->apcb1);
>>           case CRYCB_FORMAT1:
>>               return setup_apcb00(vcpu,
>>                           (unsigned long *) &crycb_s->apcb0,
>> -                        (unsigned long) &crycb->apcb0,
>> +                        crycb_gpa,
>>                           (unsigned long *) &crycb_h->apcb0);
>>           }
>>           break;
>>       case CRYCB_FORMAT0:
>> -        if ((crycb_o & PAGE_MASK) != ((crycb_o + 32) & PAGE_MASK))
>> +        if ((crycb_gpa & PAGE_MASK) != ((crycb_gpa + 32) & PAGE_MASK))
>>               return -EACCES;
>>           switch (fmt_h) {
>>           case CRYCB_FORMAT2:
>>               return setup_apcb10(vcpu, &crycb_s->apcb1,
>> -                        (unsigned long) &crycb->apcb0,
>> +                        crycb_gpa,
>>                           &crycb_h->apcb1);
>>           case CRYCB_FORMAT1:
>>           case CRYCB_FORMAT0:
>>               return setup_apcb00(vcpu,
>>                           (unsigned long *) &crycb_s->apcb0,
>> -                        (unsigned long) &crycb->apcb0,
>> +                        crycb_gpa,
>>                           (unsigned long *) &crycb_h->apcb0);
>>           }
>>       }
> 

-- 
Pierre Morel
IBM Lab Boeblingen