KVM: s390: Don't enable skeys by default

The first invocation of storage key operations on a given cpu will be intercepted.

On these intercepts we will enable storage keys for the guest and remove the
previously added intercepts.
Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/include/asm/kvm_host.h

@@ -89,6 +89,9 @@ struct kvm_s390_sie_block {
 	__u16   lctl;			/* 0x0044 */
 	__s16	icpua;			/* 0x0046 */
 #define ICTL_LPSW 0x00400000
+#define ICTL_ISKE 0x00004000
+#define ICTL_SSKE 0x00002000
+#define ICTL_RRBE 0x00001000
 	__u32	ictl;			/* 0x0048 */
 	__u32	eca;			/* 0x004c */
 	__u8	icptcode;		/* 0x0050 */

arch/s390/include/asm/mmu_context.h

@@ -23,7 +23,7 @@ static inline int init_new_context(struct task_struct *tsk,
 	mm->context.asce_bits |= _ASCE_TYPE_REGION3;
 #endif
 	mm->context.has_pgste = 0;
-	mm->context.use_skey = 1;
+	mm->context.use_skey = 0;
 	mm->context.asce_limit = STACK_TOP_MAX;
 	crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm));
 	return 0;

arch/s390/kvm/kvm-s390.c

@@ -465,6 +465,7 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
 	vcpu->arch.sie_block->ecb2  = 8;
 	vcpu->arch.sie_block->eca   = 0xC1002001U;
 	vcpu->arch.sie_block->fac   = (int) (long) vfacilities;
+	vcpu->arch.sie_block->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
 	if (kvm_enabled_cmma()) {
 		cbrl = alloc_page(GFP_KERNEL | __GFP_ZERO);
 		if (cbrl) {

arch/s390/kvm/priv.c

@@ -147,8 +147,21 @@ static int handle_store_cpu_address(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
+static void __skey_check_enable(struct kvm_vcpu *vcpu)
+{
+	if (!(vcpu->arch.sie_block->ictl & (ICTL_ISKE | ICTL_SSKE | ICTL_RRBE)))
+		return;
+
+	s390_enable_skey();
+	trace_kvm_s390_skey_related_inst(vcpu);
+	vcpu->arch.sie_block->ictl &= ~(ICTL_ISKE | ICTL_SSKE | ICTL_RRBE);
+}
+
+
 static int handle_skey(struct kvm_vcpu *vcpu)
 {
+	__skey_check_enable(vcpu);
+
 	vcpu->stat.instruction_storage_key++;
 
 	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
@@ -618,6 +631,7 @@ static int handle_pfmf(struct kvm_vcpu *vcpu)
 		}
 
 		if (vcpu->run->s.regs.gprs[reg1] & PFMF_SK) {
+			__skey_check_enable(vcpu);
 			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/kvm/trace.h

@@ -30,6 +30,20 @@
 	TP_printk("%02d[%016lx-%016lx]: " p_str, __entry->id,		\
 		  __entry->pswmask, __entry->pswaddr, p_args)
 
+TRACE_EVENT(kvm_s390_skey_related_inst,
+	    TP_PROTO(VCPU_PROTO_COMMON),
+	    TP_ARGS(VCPU_ARGS_COMMON),
+
+	    TP_STRUCT__entry(
+		    VCPU_FIELD_COMMON
+		    ),
+
+	    TP_fast_assign(
+		    VCPU_ASSIGN_COMMON
+		    ),
+	    VCPU_TP_PRINTK("%s", "first instruction related to skeys on vcpu")
+	);
+
 TRACE_EVENT(kvm_s390_major_guest_pfault,
 	    TP_PROTO(VCPU_PROTO_COMMON),
 	    TP_ARGS(VCPU_ARGS_COMMON),