Re: [PATCH v10 1/3] KVM: s390: ipte lock for SCA access should be contained in KVM

[Janosch Frank <frankja@linux.ibm.com>]

On 6/20/22 14:54, Pierre Morel wrote:
> 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.


The subject and commit description don't fit together.
You're doing two things in this patch and only describe one of them.

I'd suggest something like this:

KVM: s390: Cleanup ipte lock access and SIIF facility checks

We can check if SIIF is enabled by testing the sclp_info struct instead 
of testing the sie control block eca variable as that facility is always 
enabled if available.

Also let's cleanup all the ipte related struct member accesses which 
currently happen by referencing the KVM struct via the VCPU struct. 
Making the KVM struct the parameter to the ipte_* functions removes one 
level of indirection which makes the code more readable.


Other than that I'm happy with this patch.

> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
> Reviewed-by: David Hildenbrand <david@redhat.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 227ed0009354..082ec5f2c3a5 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,
> @@ -1086,7 +1086,7 @@ 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
> @@ -1127,7 +1127,7 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
>   	}
>   out_unlock:
>   	if (need_ipte_lock)
> -		ipte_unlock(vcpu);
> +		ipte_unlock(vcpu->kvm);
>   	if (nr_pages > ARRAY_SIZE(gpa_array))
>   		vfree(gpas);
>   	return rc;
> @@ -1199,10 +1199,10 @@ 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;
>   }
> @@ -1465,7 +1465,7 @@ 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)
> @@ -1499,7 +1499,7 @@ 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 83bb5cf97282..12c464c7cddf 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -442,7 +442,7 @@ 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;
> @@ -1471,7 +1471,7 @@ 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);
> @@ -1508,7 +1508,7 @@ 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;
>   }
>