s390/mm: disable KSM for storage key enabled pages

When storage keys are enabled unmerge already merged pages and prevent
new pages from being merged.

Signed-off-by: Dominik Dingel <[e-mail]>
Acked-by: Christian Borntraeger <[e-mail]>
Reviewed-by: Paolo Bonzini <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/include/asm/pgtable.h

···
 extern int vmem_add_mapping(unsigned long start, unsigned long size);
 extern int vmem_remove_mapping(unsigned long start, unsigned long size);
 extern int s390_enable_sie(void);
-extern void s390_enable_skey(void);
+extern int s390_enable_skey(void);
 extern void s390_reset_cmma(struct mm_struct *mm);
 
 /*

arch/s390/kvm/priv.c

···
 	return 0;
 }
 
-static void __skey_check_enable(struct kvm_vcpu *vcpu)
+static int __skey_check_enable(struct kvm_vcpu *vcpu)
 {
+	int rc = 0;
 	if (!(vcpu->arch.sie_block->ictl & (ICTL_ISKE | ICTL_SSKE | ICTL_RRBE)))
-		return;
+		return rc;
 
-	s390_enable_skey();
+	rc = s390_enable_skey();
 	trace_kvm_s390_skey_related_inst(vcpu);
 	vcpu->arch.sie_block->ictl &= ~(ICTL_ISKE | ICTL_SSKE | ICTL_RRBE);
+	return rc;
 }
 
 
 static int handle_skey(struct kvm_vcpu *vcpu)
 {
-	__skey_check_enable(vcpu);
+	int rc = __skey_check_enable(vcpu);
 
+	if (rc)
+		return rc;
 	vcpu->stat.instruction_storage_key++;
 
 	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
···
 		}
 
 		if (vcpu->run->s.regs.gprs[reg1] & PFMF_SK) {
-			__skey_check_enable(vcpu);
+			int rc = __skey_check_enable(vcpu);
+
+			if (rc)
+				return rc;
 			if (set_guest_storage_key(current->mm, useraddr,
 					vcpu->run->s.regs.gprs[reg1] & PFMF_KEY,
 					vcpu->run->s.regs.gprs[reg1] & PFMF_NQ))

arch/s390/mm/pgtable.c

···
 #include <linux/rcupdate.h>
 #include <linux/slab.h>
 #include <linux/swapops.h>
+#include <linux/ksm.h>
+#include <linux/mman.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
···
 	return 0;
 }
 
-void s390_enable_skey(void)
+int s390_enable_skey(void)
 {
 	struct mm_walk walk = { .pte_entry = __s390_enable_skey };
 	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	int rc = 0;
 
 	down_write(&mm->mmap_sem);
 	if (mm_use_skey(mm))
 		goto out_up;
 
 	mm->context.use_skey = 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;
+			rc = -ENOMEM;
+			goto out_up;
+		}
+	}
+	mm->def_flags &= ~VM_MERGEABLE;
 
 	walk.mm = mm;
 	walk_page_range(0, TASK_SIZE, &walk);
 
 out_up:
 	up_write(&mm->mmap_sem);
+	return rc;
 }
 EXPORT_SYMBOL_GPL(s390_enable_skey);