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

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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@xxxxxxxxxxxxx>



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@xxxxxxxxxxxxx>
---
  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;
  }
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