[PATCH v2 2/3] KVM: s390: Always allocate esca_block

[Christoph Schlameuss <schlameuss@linux.ibm.com>]

Instead of allocating a BSCA and upgrading it for PV or when adding the
65th cpu we can always use the ESCA.

The only downside of the change is that we will always allocate 4 pages
for a 248 cpu ESCA instead of a single page for the BSCA per VM.
In return we can delete a bunch of checks and special handling depending
on the SCA type as well as the whole BSCA to ESCA conversion.

As a fallback we can still run without SCA entries when the SIGP
interpretation facility or ESCA are not available.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/include/asm/kvm_host.h |   1 -
 arch/s390/kvm/interrupt.c        |  67 ++++-------------
 arch/s390/kvm/kvm-s390.c         | 159 ++++++---------------------------------
 arch/s390/kvm/kvm-s390.h         |   4 +-
 4 files changed, 42 insertions(+), 189 deletions(-)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index f51bac835260f562eaf4bbfd373a24bfdbc43834..d03e354a63d9c931522c1a1607eba8685c24527f 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -631,7 +631,6 @@ struct kvm_s390_pv {
 
 struct kvm_arch{
 	void *sca;
-	int use_esca;
 	rwlock_t sca_lock;
 	debug_info_t *dbf;
 	struct kvm_s390_float_interrupt float_int;
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 60c360c18690f6b94e8483dab2c25f016451204b..50f8e8167a6f0bb2f4dc2149a34b4148ccb6506f 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -51,21 +51,11 @@ static int sca_ext_call_pending(struct kvm_vcpu *vcpu, int *src_id)
 
 	BUG_ON(!kvm_s390_use_sca_entries());
 	read_lock(&vcpu->kvm->arch.sca_lock);
-	if (vcpu->kvm->arch.use_esca) {
-		struct esca_block *sca = vcpu->kvm->arch.sca;
-		union esca_sigp_ctrl sigp_ctrl =
-			sca->cpu[vcpu->vcpu_id].sigp_ctrl;
+	struct esca_block *sca = vcpu->kvm->arch.sca;
+	union esca_sigp_ctrl sigp_ctrl = sca->cpu[vcpu->vcpu_id].sigp_ctrl;
 
-		c = sigp_ctrl.c;
-		scn = sigp_ctrl.scn;
-	} else {
-		struct bsca_block *sca = vcpu->kvm->arch.sca;
-		union bsca_sigp_ctrl sigp_ctrl =
-			sca->cpu[vcpu->vcpu_id].sigp_ctrl;
-
-		c = sigp_ctrl.c;
-		scn = sigp_ctrl.scn;
-	}
+	c = sigp_ctrl.c;
+	scn = sigp_ctrl.scn;
 	read_unlock(&vcpu->kvm->arch.sca_lock);
 
 	if (src_id)
@@ -80,33 +70,17 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id)
 
 	BUG_ON(!kvm_s390_use_sca_entries());
 	read_lock(&vcpu->kvm->arch.sca_lock);
-	if (vcpu->kvm->arch.use_esca) {
-		struct esca_block *sca = vcpu->kvm->arch.sca;
-		union esca_sigp_ctrl *sigp_ctrl =
-			&(sca->cpu[vcpu->vcpu_id].sigp_ctrl);
-		union esca_sigp_ctrl new_val = {0}, old_val;
-
-		old_val = READ_ONCE(*sigp_ctrl);
-		new_val.scn = src_id;
-		new_val.c = 1;
-		old_val.c = 0;
-
-		expect = old_val.value;
-		rc = cmpxchg(&sigp_ctrl->value, old_val.value, new_val.value);
-	} else {
-		struct bsca_block *sca = vcpu->kvm->arch.sca;
-		union bsca_sigp_ctrl *sigp_ctrl =
-			&(sca->cpu[vcpu->vcpu_id].sigp_ctrl);
-		union bsca_sigp_ctrl new_val = {0}, old_val;
+	struct esca_block *sca = vcpu->kvm->arch.sca;
+	union esca_sigp_ctrl *sigp_ctrl = &sca->cpu[vcpu->vcpu_id].sigp_ctrl;
+	union esca_sigp_ctrl new_val = {0}, old_val;
 
-		old_val = READ_ONCE(*sigp_ctrl);
-		new_val.scn = src_id;
-		new_val.c = 1;
-		old_val.c = 0;
+	old_val = READ_ONCE(*sigp_ctrl);
+	new_val.scn = src_id;
+	new_val.c = 1;
+	old_val.c = 0;
 
-		expect = old_val.value;
-		rc = cmpxchg(&sigp_ctrl->value, old_val.value, new_val.value);
-	}
+	expect = old_val.value;
+	rc = cmpxchg(&sigp_ctrl->value, old_val.value, new_val.value);
 	read_unlock(&vcpu->kvm->arch.sca_lock);
 
 	if (rc != expect) {
@@ -123,19 +97,10 @@ static void sca_clear_ext_call(struct kvm_vcpu *vcpu)
 		return;
 	kvm_s390_clear_cpuflags(vcpu, CPUSTAT_ECALL_PEND);
 	read_lock(&vcpu->kvm->arch.sca_lock);
-	if (vcpu->kvm->arch.use_esca) {
-		struct esca_block *sca = vcpu->kvm->arch.sca;
-		union esca_sigp_ctrl *sigp_ctrl =
-			&(sca->cpu[vcpu->vcpu_id].sigp_ctrl);
-
-		WRITE_ONCE(sigp_ctrl->value, 0);
-	} else {
-		struct bsca_block *sca = vcpu->kvm->arch.sca;
-		union bsca_sigp_ctrl *sigp_ctrl =
-			&(sca->cpu[vcpu->vcpu_id].sigp_ctrl);
+	struct esca_block *sca = vcpu->kvm->arch.sca;
+	union esca_sigp_ctrl *sigp_ctrl = &sca->cpu[vcpu->vcpu_id].sigp_ctrl;
 
-		WRITE_ONCE(sigp_ctrl->value, 0);
-	}
+	WRITE_ONCE(sigp_ctrl->value, 0);
 	read_unlock(&vcpu->kvm->arch.sca_lock);
 }
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index b65e4cbe67cf70a7d614607ebdd679060e7d31f4..321745580c57dd21070eb5bc30ebab263da7d329 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -271,7 +271,6 @@ debug_info_t *kvm_s390_dbf_uv;
 /* forward declarations */
 static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
 			      unsigned long end);
-static int sca_switch_to_extended(struct kvm *kvm);
 
 static void kvm_clock_sync_scb(struct kvm_s390_sie_block *scb, u64 delta)
 {
@@ -631,11 +630,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_NR_VCPUS:
 	case KVM_CAP_MAX_VCPUS:
 	case KVM_CAP_MAX_VCPU_ID:
-		r = KVM_S390_BSCA_CPU_SLOTS;
+		r = KVM_S390_ESCA_CPU_SLOTS;
 		if (!kvm_s390_use_sca_entries())
 			r = KVM_MAX_VCPUS;
-		else if (sclp.has_esca && sclp.has_64bscao)
-			r = KVM_S390_ESCA_CPU_SLOTS;
 		if (ext == KVM_CAP_NR_VCPUS)
 			r = min_t(unsigned int, num_online_cpus(), r);
 		else if (ext == KVM_CAP_MAX_VCPU_ID)
@@ -1932,13 +1929,11 @@ static int kvm_s390_get_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
  * Updates the Multiprocessor Topology-Change-Report bit to signal
  * the guest with a topology change.
  * This is only relevant if the topology facility is present.
- *
- * The SCA version, bsca or esca, doesn't matter as offset is the same.
  */
 static void kvm_s390_update_topology_change_report(struct kvm *kvm, bool val)
 {
 	union sca_utility new, old;
-	struct bsca_block *sca;
+	struct esca_block *sca;
 
 	read_lock(&kvm->arch.sca_lock);
 	sca = kvm->arch.sca;
@@ -1969,7 +1964,7 @@ static int kvm_s390_get_topo_change_indication(struct kvm *kvm,
 		return -ENXIO;
 
 	read_lock(&kvm->arch.sca_lock);
-	topo = ((struct bsca_block *)kvm->arch.sca)->utility.mtcr;
+	topo = ((struct esca_block *)kvm->arch.sca)->utility.mtcr;
 	read_unlock(&kvm->arch.sca_lock);
 
 	return put_user(topo, (u8 __user *)attr->addr);
@@ -2668,14 +2663,6 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
 		if (kvm_s390_pv_is_protected(kvm))
 			break;
 
-		/*
-		 *  FMT 4 SIE needs esca. As we never switch back to bsca from
-		 *  esca, we need no cleanup in the error cases below
-		 */
-		r = sca_switch_to_extended(kvm);
-		if (r)
-			break;
-
 		r = s390_disable_cow_sharing();
 		if (r)
 			break;
@@ -3316,10 +3303,7 @@ static void kvm_s390_crypto_init(struct kvm *kvm)
 
 static void sca_dispose(struct kvm *kvm)
 {
-	if (kvm->arch.use_esca)
-		free_pages_exact(kvm->arch.sca, sizeof(struct esca_block));
-	else
-		free_page((unsigned long)(kvm->arch.sca));
+	free_pages_exact(kvm->arch.sca, sizeof(struct esca_block));
 	kvm->arch.sca = NULL;
 }
 
@@ -3333,10 +3317,9 @@ void kvm_arch_free_vm(struct kvm *kvm)
 
 int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 {
-	gfp_t alloc_flags = GFP_KERNEL_ACCOUNT;
-	int i, rc;
+	gfp_t alloc_flags = GFP_KERNEL_ACCOUNT | __GFP_ZERO;
 	char debug_name[16];
-	static unsigned long sca_offset;
+	int i, rc;
 
 	rc = -EINVAL;
 #ifdef CONFIG_KVM_S390_UCONTROL
@@ -3358,17 +3341,12 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	if (!sclp.has_64bscao)
 		alloc_flags |= GFP_DMA;
 	rwlock_init(&kvm->arch.sca_lock);
-	/* start with basic SCA */
-	kvm->arch.sca = (struct bsca_block *) get_zeroed_page(alloc_flags);
-	if (!kvm->arch.sca)
-		goto out_err;
 	mutex_lock(&kvm_lock);
-	sca_offset += 16;
-	if (sca_offset + sizeof(struct bsca_block) > PAGE_SIZE)
-		sca_offset = 0;
-	kvm->arch.sca = (struct bsca_block *)
-			((char *) kvm->arch.sca + sca_offset);
+
+	kvm->arch.sca = alloc_pages_exact(sizeof(*kvm->arch.sca), alloc_flags);
 	mutex_unlock(&kvm_lock);
+	if (!kvm->arch.sca)
+		goto out_err;
 
 	sprintf(debug_name, "kvm-%u", current->pid);
 
@@ -3550,17 +3528,10 @@ static void sca_del_vcpu(struct kvm_vcpu *vcpu)
 	if (!kvm_s390_use_sca_entries())
 		return;
 	read_lock(&vcpu->kvm->arch.sca_lock);
-	if (vcpu->kvm->arch.use_esca) {
-		struct esca_block *sca = vcpu->kvm->arch.sca;
-
-		clear_bit_inv(vcpu->vcpu_id, (unsigned long *) sca->mcn);
-		sca->cpu[vcpu->vcpu_id].sda = 0;
-	} else {
-		struct bsca_block *sca = vcpu->kvm->arch.sca;
+	struct esca_block *sca = vcpu->kvm->arch.sca;
 
-		clear_bit_inv(vcpu->vcpu_id, (unsigned long *) &sca->mcn);
-		sca->cpu[vcpu->vcpu_id].sda = 0;
-	}
+	clear_bit_inv(vcpu->vcpu_id, (unsigned long *)sca->mcn);
+	sca->cpu[vcpu->vcpu_id].sda = 0;
 	read_unlock(&vcpu->kvm->arch.sca_lock);
 }
 
@@ -3575,105 +3546,23 @@ static void sca_add_vcpu(struct kvm_vcpu *vcpu)
 		return;
 	}
 	read_lock(&vcpu->kvm->arch.sca_lock);
-	if (vcpu->kvm->arch.use_esca) {
-		struct esca_block *sca = vcpu->kvm->arch.sca;
-		phys_addr_t sca_phys = virt_to_phys(sca);
-
-		sca->cpu[vcpu->vcpu_id].sda = virt_to_phys(vcpu->arch.sie_block);
-		vcpu->arch.sie_block->scaoh = sca_phys >> 32;
-		vcpu->arch.sie_block->scaol = sca_phys & ESCA_SCAOL_MASK;
-		vcpu->arch.sie_block->ecb2 |= ECB2_ESCA;
-		set_bit_inv(vcpu->vcpu_id, (unsigned long *) sca->mcn);
-	} else {
-		struct bsca_block *sca = vcpu->kvm->arch.sca;
-		phys_addr_t sca_phys = virt_to_phys(sca);
-
-		sca->cpu[vcpu->vcpu_id].sda = virt_to_phys(vcpu->arch.sie_block);
-		vcpu->arch.sie_block->scaoh = sca_phys >> 32;
-		vcpu->arch.sie_block->scaol = sca_phys;
-		set_bit_inv(vcpu->vcpu_id, (unsigned long *) &sca->mcn);
-	}
+	struct esca_block *sca = vcpu->kvm->arch.sca;
+	phys_addr_t sca_phys = virt_to_phys(sca);
+
+	sca->cpu[vcpu->vcpu_id].sda = virt_to_phys(vcpu->arch.sie_block);
+	vcpu->arch.sie_block->scaoh = sca_phys >> 32;
+	vcpu->arch.sie_block->scaol = sca_phys & ESCA_SCAOL_MASK;
+	vcpu->arch.sie_block->ecb2 |= ECB2_ESCA;
+	set_bit_inv(vcpu->vcpu_id, (unsigned long *)sca->mcn);
 	read_unlock(&vcpu->kvm->arch.sca_lock);
 }
 
-/* Basic SCA to Extended SCA data copy routines */
-static inline void sca_copy_entry(struct esca_entry *d, struct bsca_entry *s)
-{
-	d->sda = s->sda;
-	d->sigp_ctrl.c = s->sigp_ctrl.c;
-	d->sigp_ctrl.scn = s->sigp_ctrl.scn;
-}
-
-static void sca_copy_b_to_e(struct esca_block *d, struct bsca_block *s)
-{
-	int i;
-
-	d->ipte_control = s->ipte_control;
-	d->mcn[0] = s->mcn;
-	for (i = 0; i < KVM_S390_BSCA_CPU_SLOTS; i++)
-		sca_copy_entry(&d->cpu[i], &s->cpu[i]);
-}
-
-static int sca_switch_to_extended(struct kvm *kvm)
-{
-	struct bsca_block *old_sca = kvm->arch.sca;
-	struct esca_block *new_sca;
-	struct kvm_vcpu *vcpu;
-	unsigned long vcpu_idx;
-	u32 scaol, scaoh;
-	phys_addr_t new_sca_phys;
-
-	if (kvm->arch.use_esca)
-		return 0;
-
-	new_sca = alloc_pages_exact(sizeof(*new_sca), GFP_KERNEL_ACCOUNT | __GFP_ZERO);
-	if (!new_sca)
-		return -ENOMEM;
-
-	new_sca_phys = virt_to_phys(new_sca);
-	scaoh = new_sca_phys >> 32;
-	scaol = new_sca_phys & ESCA_SCAOL_MASK;
-
-	kvm_s390_vcpu_block_all(kvm);
-	write_lock(&kvm->arch.sca_lock);
-
-	sca_copy_b_to_e(new_sca, old_sca);
-
-	kvm_for_each_vcpu(vcpu_idx, vcpu, kvm) {
-		vcpu->arch.sie_block->scaoh = scaoh;
-		vcpu->arch.sie_block->scaol = scaol;
-		vcpu->arch.sie_block->ecb2 |= ECB2_ESCA;
-	}
-	kvm->arch.sca = new_sca;
-	kvm->arch.use_esca = 1;
-
-	write_unlock(&kvm->arch.sca_lock);
-	kvm_s390_vcpu_unblock_all(kvm);
-
-	free_page((unsigned long)old_sca);
-
-	VM_EVENT(kvm, 2, "Switched to ESCA (0x%p -> 0x%p)",
-		 old_sca, kvm->arch.sca);
-	return 0;
-}
-
 static int sca_can_add_vcpu(struct kvm *kvm, unsigned int id)
 {
-	int rc;
-
-	if (!kvm_s390_use_sca_entries()) {
-		if (id < KVM_MAX_VCPUS)
-			return true;
-		return false;
-	}
-	if (id < KVM_S390_BSCA_CPU_SLOTS)
-		return true;
-	if (!sclp.has_esca || !sclp.has_64bscao)
-		return false;
-
-	rc = kvm->arch.use_esca ? 0 : sca_switch_to_extended(kvm);
+	if (!kvm_s390_use_sca_entries())
+		return id < KVM_MAX_VCPUS;
 
-	return rc == 0 && id < KVM_S390_ESCA_CPU_SLOTS;
+	return id < KVM_S390_ESCA_CPU_SLOTS;
 }
 
 /* needs disabled preemption to protect from TOD sync and vcpu_load/put */
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 8d3bbb2dd8d27802bbde2a7bd1378033ad614b8e..2c8e177e4af8f2dab07fd42a904cefdea80f6855 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -531,7 +531,7 @@ int kvm_s390_handle_per_event(struct kvm_vcpu *vcpu);
 /* support for Basic/Extended SCA handling */
 static inline union ipte_control *kvm_s390_get_ipte_control(struct kvm *kvm)
 {
-	struct bsca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */
+	struct esca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */
 
 	return &sca->ipte_control;
 }
@@ -542,7 +542,7 @@ static inline int kvm_s390_use_sca_entries(void)
 	 * might use the entries. By not setting the entries and keeping them
 	 * invalid, hardware will not access them but intercept.
 	 */
-	return sclp.has_sigpif;
+	return sclp.has_sigpif && sclp.has_esca;
 }
 void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu,
 				     struct mcck_volatile_info *mcck_info);

-- 
2.49.0