KVM: s390: : Feature and fix for kvm/next (4.8) part 4

1. Provide an exit to userspace for the invalid opcode 0 (used for
    software breakpoints)
 2. "Fix" (by returning condition code 3) some unhandled PTFF subcodes
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v2.0.14 (GNU/Linux)
 
 iQIcBAABAgAGBQJXjMzCAAoJEBF7vIC1phx8yrsP/2mM7YC/kJLHMwbWJeRF8nCa
 Du8ah4x0ocadlMkXzo/uzTl7+TIFZq0UsqN6XYp3TO1R3Z6fkbZ8RHnAd0dIwAhe
 GJl3a+L1L8dDkAhVFIxkTpS/lcpaQb6HL9PmBzprscm42nt88Cb9GUNWwhL5EwXv
 lYNUpS03VK7V/JsemeuYMfwyMtP6VNAD80LazVCoS7gboqaaAaZNMEuwEaiNcwk3
 NjdynA1mk9fpEash3p0ESCtgRwP8vytgVLLctArXOIFVuDdT0obbSmBikUiNPY5f
 7nl0yzaAkynRrzwWnZ6kBdDR1s61GsS+zZ8q4scXp7bW7TrsK7j4dlYMFQQKKvAO
 LSOS4DfNgUQ/4Z4un04PWcRjQ0kmWQFluLXyOW3SYg0ft6N8B6ujsXWui4rN3d5W
 sKAw4lnUHyKsjBKQ3zIX2YoYZXrJavxgGyQ1m91iT6oyjm0D6Ip821eAq02I9RPi
 lZRoe5rbqYxbN4485cNy81V2v3VgNOs5rsLOXwDio+U9DxvxE0uNIGKAoK6d2Nqn
 EFSlPc8SvOyvQVAFzeMBERQ4cUSAQ9p+BtBw4pr3y6Mm1AzenUCq5yLNID1oNfYq
 U5vIBIL8rVj8ffW1HRrfM3pnWwcVKAhsm5ssQxfHNYXNJ2LA5aV6LGAsdfoN+lP+
 faVW07AcCwYrKpK4TQVb
 =/3KO
 -----END PGP SIGNATURE-----

Merge tag 'kvm-s390-next-4.8-4' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into next

KVM: s390: : Feature and fix for kvm/next (4.8) part 4

1. Provide an exit to userspace for the invalid opcode 0 (used for
   software breakpoints)
2. "Fix" (by returning condition code 3) some unhandled PTFF subcodes

Documentation/virtual/kvm/api.txt

@@ -3857,6 +3857,19 @@ as a broadcast even in x2APIC mode in order to support physical x2APIC
 without interrupt remapping.  This is undesirable in logical mode,
 where 0xff represents CPUs 0-7 in cluster 0.
 
+7.8 KVM_CAP_S390_USER_INSTR0
+
+Architectures: s390
+Parameters: none
+
+With this capability enabled, all illegal instructions 0x0000 (2 bytes) will
+be intercepted and forwarded to user space. User space can use this
+mechanism e.g. to realize 2-byte software breakpoints. The kernel will
+not inject an operating exception for these instructions, user space has
+to take care of that.
+
+This capability can be enabled dynamically even if VCPUs were already
+created and are running.
 
 8. Other capabilities.
 ----------------------

arch/s390/include/asm/kvm_host.h

@@ -43,6 +43,7 @@
 /* s390-specific vcpu->requests bit members */
 #define KVM_REQ_ENABLE_IBS         8
 #define KVM_REQ_DISABLE_IBS        9
+#define KVM_REQ_ICPT_OPEREXC       10
 
 #define SIGP_CTRL_C		0x80
 #define SIGP_CTRL_SCN_MASK	0x3f
@@ -666,6 +667,7 @@ struct kvm_arch{
 	int user_cpu_state_ctrl;
 	int user_sigp;
 	int user_stsi;
+	int user_instr0;
 	struct s390_io_adapter *adapters[MAX_S390_IO_ADAPTERS];
 	wait_queue_head_t ipte_wq;
 	int ipte_lock_count;

arch/s390/kvm/intercept.c

@@ -359,6 +359,9 @@ static int handle_operexc(struct kvm_vcpu *vcpu)
 	    test_kvm_facility(vcpu->kvm, 74))
 		return handle_sthyi(vcpu);
 
+	if (vcpu->arch.sie_block->ipa == 0 && vcpu->kvm->arch.user_instr0)
+		return -EOPNOTSUPP;
+
 	return kvm_s390_inject_program_int(vcpu, PGM_OPERATION);
 }
 

arch/s390/kvm/kvm-s390.c

@@ -364,6 +364,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_S390_USER_STSI:
 	case KVM_CAP_S390_SKEYS:
 	case KVM_CAP_S390_IRQ_STATE:
+	case KVM_CAP_S390_USER_INSTR0:
 		r = 1;
 		break;
 	case KVM_CAP_S390_MEM_OP:
@@ -456,6 +457,16 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 	return r;
 }
 
+static void icpt_operexc_on_all_vcpus(struct kvm *kvm)
+{
+	unsigned int i;
+	struct kvm_vcpu *vcpu;
+
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		kvm_s390_sync_request(KVM_REQ_ICPT_OPEREXC, vcpu);
+	}
+}
+
 static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
 {
 	int r;
@@ -507,6 +518,12 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
 		kvm->arch.user_stsi = 1;
 		r = 0;
 		break;
+	case KVM_CAP_S390_USER_INSTR0:
+		VM_EVENT(kvm, 3, "%s", "ENABLE: CAP_S390_USER_INSTR0");
+		kvm->arch.user_instr0 = 1;
+		icpt_operexc_on_all_vcpus(kvm);
+		r = 0;
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -1836,6 +1853,8 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 		vcpu->arch.gmap = vcpu->kvm->arch.gmap;
 		sca_add_vcpu(vcpu);
 	}
+	if (test_kvm_facility(vcpu->kvm, 74) || vcpu->kvm->arch.user_instr0)
+		vcpu->arch.sie_block->ictl |= ICTL_OPEREXC;
 	/* make vcpu_load load the right gmap on the first trigger */
 	vcpu->arch.enabled_gmap = vcpu->arch.gmap;
 }
@@ -1923,8 +1942,6 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
 	}
 	vcpu->arch.sie_block->riccbd = (unsigned long) &vcpu->run->s.regs.riccb;
 	vcpu->arch.sie_block->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
-	if (test_kvm_facility(vcpu->kvm, 74))
-		vcpu->arch.sie_block->ictl |= ICTL_OPEREXC;
 
 	if (vcpu->kvm->arch.use_cmma) {
 		rc = kvm_s390_vcpu_setup_cmma(vcpu);
@@ -2369,6 +2386,11 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
 		goto retry;
 	}
 
+	if (kvm_check_request(KVM_REQ_ICPT_OPEREXC, vcpu)) {
+		vcpu->arch.sie_block->ictl |= ICTL_OPEREXC;
+		goto retry;
+	}
+
 	/* nothing to do, just clear the request */
 	clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
 

arch/s390/kvm/priv.c

@@ -1185,7 +1185,15 @@ static int handle_sckpf(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
+static int handle_ptff(struct kvm_vcpu *vcpu)
+{
+	/* we don't emulate any control instructions yet */
+	kvm_s390_set_psw_cc(vcpu, 3);
+	return 0;
+}
+
 static const intercept_handler_t x01_handlers[256] = {
+	[0x04] = handle_ptff,
 	[0x07] = handle_sckpf,
 };
 

include/uapi/linux/kvm.h

@@ -867,6 +867,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_VCPU_ATTRIBUTES 127
 #define KVM_CAP_MAX_VCPU_ID 128
 #define KVM_CAP_X2APIC_API 129
+#define KVM_CAP_S390_USER_INSTR0 130
 
 #ifdef KVM_CAP_IRQ_ROUTING