Re: [PATCH v9 1/3] s390x: KVM: ipte lock for SCA access should be contained in KVM

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

On 5/12/22 13:32, Janosch Frank wrote:
> On 5/6/22 11:24, Pierre Morel wrote:
>> The former check to chose between SIIF or not SIIF can be done
>> using the sclp.has_siif instead of accessing per vCPU structures
> 
> Maybe replace this paragraph with:
> We can check if SIIF is enabled by testing the sclp_info struct instead 
> of testing the sie control block eca variable. sclp.has_ssif is the only 
> requirement to set ECA_SII anyway so we can go straight to the source 
> for that.
> 
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

OK, thanks,

Regards,
Pierre

> 
>>
>> When accessing the SCA, ipte lock and ipte_unlock do not need
>> to access any vcpu structures but only the KVM structure.
>>
>> Let's simplify the ipte handling.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> ---
>>   arch/s390/kvm/gaccess.c | 96 ++++++++++++++++++++---------------------
>>   arch/s390/kvm/gaccess.h |  6 +--
>>   arch/s390/kvm/priv.c    |  6 +--
>>   3 files changed, 54 insertions(+), 54 deletions(-)
>>
>> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
>> index d53a183c2005..0e1f6dd31882 100644
>> --- a/arch/s390/kvm/gaccess.c
>> +++ b/arch/s390/kvm/gaccess.c
>> @@ -262,77 +262,77 @@ struct aste {
>>       /* .. more fields there */
>>   };
>> -int ipte_lock_held(struct kvm_vcpu *vcpu)
>> +int ipte_lock_held(struct kvm *kvm)
>>   {
>> -    if (vcpu->arch.sie_block->eca & ECA_SII) {
>> +    if (sclp.has_siif) {
>>           int rc;
>> -        read_lock(&vcpu->kvm->arch.sca_lock);
>> -        rc = kvm_s390_get_ipte_control(vcpu->kvm)->kh != 0;
>> -        read_unlock(&vcpu->kvm->arch.sca_lock);
>> +        read_lock(&kvm->arch.sca_lock);
>> +        rc = kvm_s390_get_ipte_control(kvm)->kh != 0;
>> +        read_unlock(&kvm->arch.sca_lock);
>>           return rc;
>>       }
>> -    return vcpu->kvm->arch.ipte_lock_count != 0;
>> +    return kvm->arch.ipte_lock_count != 0;
>>   }
>> -static void ipte_lock_simple(struct kvm_vcpu *vcpu)
>> +static void ipte_lock_simple(struct kvm *kvm)
>>   {
>>       union ipte_control old, new, *ic;
>> -    mutex_lock(&vcpu->kvm->arch.ipte_mutex);
>> -    vcpu->kvm->arch.ipte_lock_count++;
>> -    if (vcpu->kvm->arch.ipte_lock_count > 1)
>> +    mutex_lock(&kvm->arch.ipte_mutex);
>> +    kvm->arch.ipte_lock_count++;
>> +    if (kvm->arch.ipte_lock_count > 1)
>>           goto out;
>>   retry:
>> -    read_lock(&vcpu->kvm->arch.sca_lock);
>> -    ic = kvm_s390_get_ipte_control(vcpu->kvm);
>> +    read_lock(&kvm->arch.sca_lock);
>> +    ic = kvm_s390_get_ipte_control(kvm);
>>       do {
>>           old = READ_ONCE(*ic);
>>           if (old.k) {
>> -            read_unlock(&vcpu->kvm->arch.sca_lock);
>> +            read_unlock(&kvm->arch.sca_lock);
>>               cond_resched();
>>               goto retry;
>>           }
>>           new = old;
>>           new.k = 1;
>>       } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
>> -    read_unlock(&vcpu->kvm->arch.sca_lock);
>> +    read_unlock(&kvm->arch.sca_lock);
>>   out:
>> -    mutex_unlock(&vcpu->kvm->arch.ipte_mutex);
>> +    mutex_unlock(&kvm->arch.ipte_mutex);
>>   }
>> -static void ipte_unlock_simple(struct kvm_vcpu *vcpu)
>> +static void ipte_unlock_simple(struct kvm *kvm)
>>   {
>>       union ipte_control old, new, *ic;
>> -    mutex_lock(&vcpu->kvm->arch.ipte_mutex);
>> -    vcpu->kvm->arch.ipte_lock_count--;
>> -    if (vcpu->kvm->arch.ipte_lock_count)
>> +    mutex_lock(&kvm->arch.ipte_mutex);
>> +    kvm->arch.ipte_lock_count--;
>> +    if (kvm->arch.ipte_lock_count)
>>           goto out;
>> -    read_lock(&vcpu->kvm->arch.sca_lock);
>> -    ic = kvm_s390_get_ipte_control(vcpu->kvm);
>> +    read_lock(&kvm->arch.sca_lock);
>> +    ic = kvm_s390_get_ipte_control(kvm);
>>       do {
>>           old = READ_ONCE(*ic);
>>           new = old;
>>           new.k = 0;
>>       } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
>> -    read_unlock(&vcpu->kvm->arch.sca_lock);
>> -    wake_up(&vcpu->kvm->arch.ipte_wq);
>> +    read_unlock(&kvm->arch.sca_lock);
>> +    wake_up(&kvm->arch.ipte_wq);
>>   out:
>> -    mutex_unlock(&vcpu->kvm->arch.ipte_mutex);
>> +    mutex_unlock(&kvm->arch.ipte_mutex);
>>   }
>> -static void ipte_lock_siif(struct kvm_vcpu *vcpu)
>> +static void ipte_lock_siif(struct kvm *kvm)
>>   {
>>       union ipte_control old, new, *ic;
>>   retry:
>> -    read_lock(&vcpu->kvm->arch.sca_lock);
>> -    ic = kvm_s390_get_ipte_control(vcpu->kvm);
>> +    read_lock(&kvm->arch.sca_lock);
>> +    ic = kvm_s390_get_ipte_control(kvm);
>>       do {
>>           old = READ_ONCE(*ic);
>>           if (old.kg) {
>> -            read_unlock(&vcpu->kvm->arch.sca_lock);
>> +            read_unlock(&kvm->arch.sca_lock);
>>               cond_resched();
>>               goto retry;
>>           }
>> @@ -340,15 +340,15 @@ static void ipte_lock_siif(struct kvm_vcpu *vcpu)
>>           new.k = 1;
>>           new.kh++;
>>       } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
>> -    read_unlock(&vcpu->kvm->arch.sca_lock);
>> +    read_unlock(&kvm->arch.sca_lock);
>>   }
>> -static void ipte_unlock_siif(struct kvm_vcpu *vcpu)
>> +static void ipte_unlock_siif(struct kvm *kvm)
>>   {
>>       union ipte_control old, new, *ic;
>> -    read_lock(&vcpu->kvm->arch.sca_lock);
>> -    ic = kvm_s390_get_ipte_control(vcpu->kvm);
>> +    read_lock(&kvm->arch.sca_lock);
>> +    ic = kvm_s390_get_ipte_control(kvm);
>>       do {
>>           old = READ_ONCE(*ic);
>>           new = old;
>> @@ -356,25 +356,25 @@ static void ipte_unlock_siif(struct kvm_vcpu *vcpu)
>>           if (!new.kh)
>>               new.k = 0;
>>       } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
>> -    read_unlock(&vcpu->kvm->arch.sca_lock);
>> +    read_unlock(&kvm->arch.sca_lock);
>>       if (!new.kh)
>> -        wake_up(&vcpu->kvm->arch.ipte_wq);
>> +        wake_up(&kvm->arch.ipte_wq);
>>   }
>> -void ipte_lock(struct kvm_vcpu *vcpu)
>> +void ipte_lock(struct kvm *kvm)
>>   {
>> -    if (vcpu->arch.sie_block->eca & ECA_SII)
>> -        ipte_lock_siif(vcpu);
>> +    if (sclp.has_siif)
>> +        ipte_lock_siif(kvm);
>>       else
>> -        ipte_lock_simple(vcpu);
>> +        ipte_lock_simple(kvm);
>>   }
>> -void ipte_unlock(struct kvm_vcpu *vcpu)
>> +void ipte_unlock(struct kvm *kvm)
>>   {
>> -    if (vcpu->arch.sie_block->eca & ECA_SII)
>> -        ipte_unlock_siif(vcpu);
>> +    if (sclp.has_siif)
>> +        ipte_unlock_siif(kvm);
>>       else
>> -        ipte_unlock_simple(vcpu);
>> +        ipte_unlock_simple(kvm);
>>   }
>>   static int ar_translation(struct kvm_vcpu *vcpu, union asce *asce, 
>> u8 ar,
>> @@ -1075,7 +1075,7 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, 
>> unsigned long ga, u8 ar,
>>       try_storage_prot_override = storage_prot_override_applicable(vcpu);
>>       need_ipte_lock = psw_bits(*psw).dat && !asce.r;
>>       if (need_ipte_lock)
>> -        ipte_lock(vcpu);
>> +        ipte_lock(vcpu->kvm);
>>       /*
>>        * Since we do the access further down ultimately via a move 
>> instruction
>>        * that does key checking and returns an error in case of a 
>> protection
>> @@ -1113,7 +1113,7 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, 
>> unsigned long ga, u8 ar,
>>           rc = trans_exc(vcpu, rc, ga, ar, mode, prot);
>>   out_unlock:
>>       if (need_ipte_lock)
>> -        ipte_unlock(vcpu);
>> +        ipte_unlock(vcpu->kvm);
>>       if (nr_pages > ARRAY_SIZE(gpa_array))
>>           vfree(gpas);
>>       return rc;
>> @@ -1185,10 +1185,10 @@ int check_gva_range(struct kvm_vcpu *vcpu, 
>> unsigned long gva, u8 ar,
>>       rc = get_vcpu_asce(vcpu, &asce, gva, ar, mode);
>>       if (rc)
>>           return rc;
>> -    ipte_lock(vcpu);
>> +    ipte_lock(vcpu->kvm);
>>       rc = guest_range_to_gpas(vcpu, gva, ar, NULL, length, asce, mode,
>>                    access_key);
>> -    ipte_unlock(vcpu);
>> +    ipte_unlock(vcpu->kvm);
>>       return rc;
>>   }
>> @@ -1451,7 +1451,7 @@ int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, 
>> struct gmap *sg,
>>        * tables/pointers we read stay valid - unshadowing is however
>>        * always possible - only guest_table_lock protects us.
>>        */
>> -    ipte_lock(vcpu);
>> +    ipte_lock(vcpu->kvm);
>>       rc = gmap_shadow_pgt_lookup(sg, saddr, &pgt, &dat_protection, 
>> &fake);
>>       if (rc)
>> @@ -1485,7 +1485,7 @@ int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, 
>> struct gmap *sg,
>>       pte.p |= dat_protection;
>>       if (!rc)
>>           rc = gmap_shadow_page(sg, saddr, __pte(pte.val));
>> -    ipte_unlock(vcpu);
>> +    ipte_unlock(vcpu->kvm);
>>       mmap_read_unlock(sg->mm);
>>       return rc;
>>   }
>> diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h
>> index 1124ff282012..9408d6cc8e2c 100644
>> --- a/arch/s390/kvm/gaccess.h
>> +++ b/arch/s390/kvm/gaccess.h
>> @@ -440,9 +440,9 @@ int read_guest_real(struct kvm_vcpu *vcpu, 
>> unsigned long gra, void *data,
>>       return access_guest_real(vcpu, gra, data, len, 0);
>>   }
>> -void ipte_lock(struct kvm_vcpu *vcpu);
>> -void ipte_unlock(struct kvm_vcpu *vcpu);
>> -int ipte_lock_held(struct kvm_vcpu *vcpu);
>> +void ipte_lock(struct kvm *kvm);
>> +void ipte_unlock(struct kvm *kvm);
>> +int ipte_lock_held(struct kvm *kvm);
>>   int kvm_s390_check_low_addr_prot_real(struct kvm_vcpu *vcpu, 
>> unsigned long gra);
>>   /* MVPG PEI indication bits */
>> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
>> index 5beb7a4a11b3..0e8603acc105 100644
>> --- a/arch/s390/kvm/priv.c
>> +++ b/arch/s390/kvm/priv.c
>> @@ -443,7 +443,7 @@ static int handle_ipte_interlock(struct kvm_vcpu 
>> *vcpu)
>>       vcpu->stat.instruction_ipte_interlock++;
>>       if (psw_bits(vcpu->arch.sie_block->gpsw).pstate)
>>           return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
>> -    wait_event(vcpu->kvm->arch.ipte_wq, !ipte_lock_held(vcpu));
>> +    wait_event(vcpu->kvm->arch.ipte_wq, !ipte_lock_held(vcpu->kvm));
>>       kvm_s390_retry_instr(vcpu);
>>       VCPU_EVENT(vcpu, 4, "%s", "retrying ipte interlock operation");
>>       return 0;
>> @@ -1472,7 +1472,7 @@ static int handle_tprot(struct kvm_vcpu *vcpu)
>>       access_key = (operand2 & 0xf0) >> 4;
>>       if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_DAT)
>> -        ipte_lock(vcpu);
>> +        ipte_lock(vcpu->kvm);
>>       ret = guest_translate_address_with_key(vcpu, address, ar, &gpa,
>>                              GACC_STORE, access_key);
>> @@ -1509,7 +1509,7 @@ static int handle_tprot(struct kvm_vcpu *vcpu)
>>       }
>>       if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_DAT)
>> -        ipte_unlock(vcpu);
>> +        ipte_unlock(vcpu->kvm);
>>       return ret;
>>   }
> 

-- 
Pierre Morel
IBM Lab Boeblingen