KVM: s390: Add storage key facility interpretation control

Up to now we always expected to have the storage key facility
available for our (non-VSIE) KVM guests. For huge page support, we
need to be able to disable it, so let's introduce that now.

We add the use_skf variable to manage KVM storage key facility
usage. Also we rename use_skey in the mm context struct to uses_skeys
to make it more clear that it is an indication that the vm actively
uses storage keys.
Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Reviewed-by: Farhan Ali <alifm@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/include/asm/kvm_host.h

@@ -812,6 +812,7 @@ struct kvm_arch{
 	int use_irqchip;
 	int use_cmma;
 	int use_pfmfi;
+	int use_skf;
 	int user_cpu_state_ctrl;
 	int user_sigp;
 	int user_stsi;

arch/s390/include/asm/mmu.h

@@ -21,7 +21,7 @@ typedef struct {
 	/* The mmu context uses extended page tables. */
 	unsigned int has_pgste:1;
 	/* The mmu context uses storage keys. */
-	unsigned int use_skey:1;
+	unsigned int uses_skeys:1;
 	/* The mmu context uses CMM. */
 	unsigned int uses_cmm:1;
 } mm_context_t;

arch/s390/include/asm/mmu_context.h

@@ -30,7 +30,7 @@ static inline int init_new_context(struct task_struct *tsk,
 		test_thread_flag(TIF_PGSTE) ||
 		(current->mm && current->mm->context.alloc_pgste);
 	mm->context.has_pgste = 0;
-	mm->context.use_skey = 0;
+	mm->context.uses_skeys = 0;
 	mm->context.uses_cmm = 0;
 #endif
 	switch (mm->context.asce_limit) {

arch/s390/include/asm/pgtable.h

@@ -507,10 +507,10 @@ static inline int mm_alloc_pgste(struct mm_struct *mm)
  * faults should no longer be backed by zero pages
  */
 #define mm_forbids_zeropage mm_has_pgste
-static inline int mm_use_skey(struct mm_struct *mm)
+static inline int mm_uses_skeys(struct mm_struct *mm)
 {
 #ifdef CONFIG_PGSTE
-	if (mm->context.use_skey)
+	if (mm->context.uses_skeys)
 		return 1;
 #endif
 	return 0;

arch/s390/kvm/kvm-s390.c

@@ -1493,7 +1493,7 @@ static long kvm_s390_get_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
 		return -EINVAL;
 
 	/* Is this guest using storage keys? */
-	if (!mm_use_skey(current->mm))
+	if (!mm_uses_skeys(current->mm))
 		return KVM_S390_GET_SKEYS_NONE;
 
 	/* Enforce sane limit on memory allocation */
@@ -2066,6 +2066,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	kvm->arch.css_support = 0;
 	kvm->arch.use_irqchip = 0;
 	kvm->arch.use_pfmfi = sclp.has_pfmfi;
+	kvm->arch.use_skf = sclp.has_skey;
 	kvm->arch.epoch = 0;
 
 	spin_lock_init(&kvm->arch.start_stop_lock);

arch/s390/kvm/priv.c

@@ -205,24 +205,28 @@ static int handle_store_cpu_address(struct kvm_vcpu *vcpu)
 
 int kvm_s390_skey_check_enable(struct kvm_vcpu *vcpu)
 {
-	int rc = 0;
+	int rc;
 	struct kvm_s390_sie_block *sie_block = vcpu->arch.sie_block;
 
 	trace_kvm_s390_skey_related_inst(vcpu);
-	if (!(sie_block->ictl & (ICTL_ISKE | ICTL_SSKE | ICTL_RRBE)) &&
+	/* Already enabled? */
+	if (vcpu->kvm->arch.use_skf &&
+	    !(sie_block->ictl & (ICTL_ISKE | ICTL_SSKE | ICTL_RRBE)) &&
 	    !kvm_s390_test_cpuflags(vcpu, CPUSTAT_KSS))
-		return rc;
+		return 0;
 
 	rc = s390_enable_skey();
 	VCPU_EVENT(vcpu, 3, "enabling storage keys for guest: %d", rc);
-	if (!rc) {
-		if (kvm_s390_test_cpuflags(vcpu, CPUSTAT_KSS))
-			kvm_s390_clear_cpuflags(vcpu, CPUSTAT_KSS);
-		else
-			sie_block->ictl &= ~(ICTL_ISKE | ICTL_SSKE |
-					     ICTL_RRBE);
-	}
-	return rc;
+	if (rc)
+		return rc;
+
+	if (kvm_s390_test_cpuflags(vcpu, CPUSTAT_KSS))
+		kvm_s390_clear_cpuflags(vcpu, CPUSTAT_KSS);
+	if (!vcpu->kvm->arch.use_skf)
+		sie_block->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
+	else
+		sie_block->ictl &= ~(ICTL_ISKE | ICTL_SSKE | ICTL_RRBE);
+	return 0;
 }
 
 static int try_handle_skey(struct kvm_vcpu *vcpu)
@@ -232,7 +236,7 @@ static int try_handle_skey(struct kvm_vcpu *vcpu)
 	rc = kvm_s390_skey_check_enable(vcpu);
 	if (rc)
 		return rc;
-	if (sclp.has_skey) {
+	if (vcpu->kvm->arch.use_skf) {
 		/* with storage-key facility, SIE interprets it for us */
 		kvm_s390_retry_instr(vcpu);
 		VCPU_EVENT(vcpu, 4, "%s", "retrying storage key operation");

arch/s390/mm/gmap.c

@@ -2184,14 +2184,14 @@ int s390_enable_skey(void)
 	int rc = 0;
 
 	down_write(&mm->mmap_sem);
-	if (mm_use_skey(mm))
+	if (mm_uses_skeys(mm))
 		goto out_up;
 
-	mm->context.use_skey = 1;
+	mm->context.uses_skeys = 1;
 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
 		if (ksm_madvise(vma, vma->vm_start, vma->vm_end,
 				MADV_UNMERGEABLE, &vma->vm_flags)) {
-			mm->context.use_skey = 0;
+			mm->context.uses_skeys = 0;
 			rc = -ENOMEM;
 			goto out_up;
 		}

arch/s390/mm/pgtable.c

@@ -158,7 +158,7 @@ static inline pgste_t pgste_update_all(pte_t pte, pgste_t pgste,
 #ifdef CONFIG_PGSTE
 	unsigned long address, bits, skey;
 
-	if (!mm_use_skey(mm) || pte_val(pte) & _PAGE_INVALID)
+	if (!mm_uses_skeys(mm) || pte_val(pte) & _PAGE_INVALID)
 		return pgste;
 	address = pte_val(pte) & PAGE_MASK;
 	skey = (unsigned long) page_get_storage_key(address);
@@ -180,7 +180,7 @@ static inline void pgste_set_key(pte_t *ptep, pgste_t pgste, pte_t entry,
 	unsigned long address;
 	unsigned long nkey;
 
-	if (!mm_use_skey(mm) || pte_val(entry) & _PAGE_INVALID)
+	if (!mm_uses_skeys(mm) || pte_val(entry) & _PAGE_INVALID)
 		return;
 	VM_BUG_ON(!(pte_val(*ptep) & _PAGE_INVALID));
 	address = pte_val(entry) & PAGE_MASK;