KVM: s390: interface to query and configure cpu subfunctions

We have certain instructions that indicate available subfunctions via
a query subfunction (crypto functions and ptff), or via a test bit
function (plo).

By exposing these "subfunction blocks" to user space, we allow user space
to
1) query available subfunctions and make sure subfunctions won't get lost
   during migration - e.g. properly indicate them via a CPU model
2) change the subfunctions to be reported to the guest (even adding
   unavailable ones)

This mechanism works just like the way we indicate the stfl(e) list to
user space.

This way, user space could even emulate some subfunctions in QEMU in the
future. If this is ever applicable, we have to make sure later on, that
unsupported subfunctions result in an intercept to QEMU.

Please note that support to indicate them to the guest is still missing
and requires hardware support. Usually, the IBC takes already care of these
subfunctions for migration safety. QEMU should make sure to always set
these bits properly according to the machine generation to be emulated.

Available subfunctions are only valid in combination with STFLE bits
retrieved via KVM_S390_VM_CPU_MACHINE and enabled via
KVM_S390_VM_CPU_PROCESSOR. If the applicable bits are available, the
indicated subfunctions are guaranteed to be correct.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

2 files changed, 109 insertions, 0 deletions

diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 789c4e27e294..f0818d70d73d 100644
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -102,6 +102,26 @@ struct kvm_s390_vm_cpu_feat {
 	__u64 feat[16];
 };
 
+#define KVM_S390_VM_CPU_PROCESSOR_SUBFUNC	4
+#define KVM_S390_VM_CPU_MACHINE_SUBFUNC		5
+/* for "test bit" instructions MSB 0 bit ordering, for "query" raw blocks */
+struct kvm_s390_vm_cpu_subfunc {
+	__u8 plo[32];		/* always */
+	__u8 ptff[16];		/* with TOD-clock steering */
+	__u8 kmac[16];		/* with MSA */
+	__u8 kmc[16];		/* with MSA */
+	__u8 km[16];		/* with MSA */
+	__u8 kimd[16];		/* with MSA */
+	__u8 klmd[16];		/* with MSA */
+	__u8 pckmo[16];		/* with MSA3 */
+	__u8 kmctr[16];		/* with MSA4 */
+	__u8 kmf[16];		/* with MSA4 */
+	__u8 kmo[16];		/* with MSA4 */
+	__u8 pcc[16];		/* with MSA4 */
+	__u8 ppno[16];		/* with MSA5 */
+	__u8 reserved[1824];
+};
+
 /* kvm attributes for crypto */
 #define KVM_S390_VM_CRYPTO_ENABLE_AES_KW	0
 #define KVM_S390_VM_CRYPTO_ENABLE_DEA_KW	1
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 2b5c14da3227..f746a35e3950 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -36,6 +36,8 @@
 #include <asm/switch_to.h>
 #include <asm/isc.h>
 #include <asm/sclp.h>
+#include <asm/cpacf.h>
+#include <asm/etr.h>
 #include "kvm-s390.h"
 #include "gaccess.h"
 
@@ -135,6 +137,8 @@ unsigned long kvm_s390_fac_list_mask_size(void)
 
 /* available cpu features supported by kvm */
 static DECLARE_BITMAP(kvm_s390_available_cpu_feat, KVM_S390_VM_CPU_FEAT_NR_BITS);
+/* available subfunctions indicated via query / "test bit" */
+static struct kvm_s390_vm_cpu_subfunc kvm_s390_available_subfunc;
 
 static struct gmap_notifier gmap_notifier;
 debug_info_t *kvm_s390_dbf;
@@ -198,8 +202,52 @@ static void allow_cpu_feat(unsigned long nr)
 	set_bit_inv(nr, kvm_s390_available_cpu_feat);
 }
 
+static inline int plo_test_bit(unsigned char nr)
+{
+	register unsigned long r0 asm("0") = (unsigned long) nr | 0x100;
+	int cc = 3; /* subfunction not available */
+
+	asm volatile(
+		/* Parameter registers are ignored for "test bit" */
+		"	plo	0,0,0,0(0)\n"
+		"	ipm	%0\n"
+		"	srl	%0,28\n"
+		: "=d" (cc)
+		: "d" (r0)
+		: "cc");
+	return cc == 0;
+}
+
 static void kvm_s390_cpu_feat_init(void)
 {
+	int i;
+
+	for (i = 0; i < 256; ++i) {
+		if (plo_test_bit(i))
+			kvm_s390_available_subfunc.plo[i >> 3] |= 0x80 >> (i & 7);
+	}
+
+	if (test_facility(28)) /* TOD-clock steering */
+		etr_ptff(kvm_s390_available_subfunc.ptff, ETR_PTFF_QAF);
+
+	if (test_facility(17)) { /* MSA */
+		__cpacf_query(CPACF_KMAC, kvm_s390_available_subfunc.kmac);
+		__cpacf_query(CPACF_KMC, kvm_s390_available_subfunc.kmc);
+		__cpacf_query(CPACF_KM, kvm_s390_available_subfunc.km);
+		__cpacf_query(CPACF_KIMD, kvm_s390_available_subfunc.kimd);
+		__cpacf_query(CPACF_KLMD, kvm_s390_available_subfunc.klmd);
+	}
+	if (test_facility(76)) /* MSA3 */
+		__cpacf_query(CPACF_PCKMO, kvm_s390_available_subfunc.pckmo);
+	if (test_facility(77)) { /* MSA4 */
+		__cpacf_query(CPACF_KMCTR, kvm_s390_available_subfunc.kmctr);
+		__cpacf_query(CPACF_KMF, kvm_s390_available_subfunc.kmf);
+		__cpacf_query(CPACF_KMO, kvm_s390_available_subfunc.kmo);
+		__cpacf_query(CPACF_PCC, kvm_s390_available_subfunc.pcc);
+	}
+	if (test_facility(57)) /* MSA5 */
+		__cpacf_query(CPACF_PPNO, kvm_s390_available_subfunc.ppno);
+
 	if (MACHINE_HAS_ESOP)
 		allow_cpu_feat(KVM_S390_VM_CPU_FEAT_ESOP);
 }
@@ -717,6 +765,16 @@ static int kvm_s390_set_processor_feat(struct kvm *kvm,
 	return ret;
 }
 
+static int kvm_s390_set_processor_subfunc(struct kvm *kvm,
+					  struct kvm_device_attr *attr)
+{
+	/*
+	 * Once supported by kernel + hw, we have to store the subfunctions
+	 * in kvm->arch and remember that user space configured them.
+	 */
+	return -ENXIO;
+}
+
 static int kvm_s390_set_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
 {
 	int ret = -ENXIO;
@@ -728,6 +786,9 @@ static int kvm_s390_set_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
 	case KVM_S390_VM_CPU_PROCESSOR_FEAT:
 		ret = kvm_s390_set_processor_feat(kvm, attr);
 		break;
+	case KVM_S390_VM_CPU_PROCESSOR_SUBFUNC:
+		ret = kvm_s390_set_processor_subfunc(kvm, attr);
+		break;
 	}
 	return ret;
 }
@@ -801,6 +862,25 @@ static int kvm_s390_get_machine_feat(struct kvm *kvm,
 	return 0;
 }
 
+static int kvm_s390_get_processor_subfunc(struct kvm *kvm,
+					  struct kvm_device_attr *attr)
+{
+	/*
+	 * Once we can actually configure subfunctions (kernel + hw support),
+	 * we have to check if they were already set by user space, if so copy
+	 * them from kvm->arch.
+	 */
+	return -ENXIO;
+}
+
+static int kvm_s390_get_machine_subfunc(struct kvm *kvm,
+					struct kvm_device_attr *attr)
+{
+	if (copy_to_user((void __user *)attr->addr, &kvm_s390_available_subfunc,
+	    sizeof(struct kvm_s390_vm_cpu_subfunc)))
+		return -EFAULT;
+	return 0;
+}
 static int kvm_s390_get_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
 {
 	int ret = -ENXIO;
@@ -818,6 +898,12 @@ static int kvm_s390_get_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
 	case KVM_S390_VM_CPU_MACHINE_FEAT:
 		ret = kvm_s390_get_machine_feat(kvm, attr);
 		break;
+	case KVM_S390_VM_CPU_PROCESSOR_SUBFUNC:
+		ret = kvm_s390_get_processor_subfunc(kvm, attr);
+		break;
+	case KVM_S390_VM_CPU_MACHINE_SUBFUNC:
+		ret = kvm_s390_get_machine_subfunc(kvm, attr);
+		break;
 	}
 	return ret;
 }
@@ -903,8 +989,11 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 		case KVM_S390_VM_CPU_MACHINE:
 		case KVM_S390_VM_CPU_PROCESSOR_FEAT:
 		case KVM_S390_VM_CPU_MACHINE_FEAT:
+		case KVM_S390_VM_CPU_MACHINE_SUBFUNC:
 			ret = 0;
 			break;
+		/* configuring subfunctions is not supported yet */
+		case KVM_S390_VM_CPU_PROCESSOR_SUBFUNC:
 		default:
 			ret = -ENXIO;
 			break;