Index: cpu.c
===================================================================
RCS file: /cvs/src/sys/arch/arm64/arm64/cpu.c,v
retrieving revision 1.99
diff -u -p -r1.99 cpu.c
--- cpu.c	24 Oct 2023 13:20:09 -0000	1.99
+++ cpu.c	10 Nov 2023 19:04:36 -0000
@@ -17,6 +17,8 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include "kstat.h"
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/proc.h>
@@ -25,6 +27,7 @@
 #include <sys/sysctl.h>
 #include <sys/task.h>
 #include <sys/user.h>
+#include <sys/kstat.h>
 
 #include <uvm/uvm.h>
 
@@ -250,6 +253,10 @@ void	cpu_psci_init(struct cpu_info *);
 void	cpu_flush_bp_noop(void);
 void	cpu_flush_bp_psci(void);
 
+#if NKSTAT > 0
+void	cpu_kstat_attach(struct cpu_info *ci);
+#endif
+
 void
 cpu_identify(struct cpu_info *ci)
 {
@@ -947,6 +954,10 @@ cpu_attach(struct device *parent, struct
 
 	cpu_psci_init(ci);
 
+#if NKSTAT > 0
+	cpu_kstat_attach(ci);
+#endif
+
 	printf("\n");
 }
 
@@ -1817,3 +1828,114 @@ cpu_psci_init(struct cpu_info *ci)
 	ci->ci_psci_suspend_param =
 		OF_getpropint(node, "arm,psci-suspend-param", 0);
 }
+
+#if NKSTAT > 0
+
+struct cpu_kstats {
+	struct kstat_kv		ck_device;
+	struct kstat_kv		ck_impl;
+	struct kstat_kv		ck_part;
+	struct kstat_kv		ck_var;
+	struct kstat_kv		ck_rev;
+
+	struct kstat_kv		ck_freq;
+	struct kstat_kv		ck_mv;
+};
+
+int
+cpu_kstat_read(struct kstat *ks)
+{
+	struct cpu_kstats *ck = ks->ks_data;
+
+        /*
+	 * this is called from an arbitrary cpu via an ioctl syscall,
+	 * and without KERNEL_LOCK held.
+	 */
+
+	kstat_kv_u32(&ck->ck_freq) = arc4random();
+	kstat_kv_u32(&ck->ck_mv) = arc4random();
+
+	getnanouptime(&ks->ks_updated); /* accuracy is not important here */
+
+	return (0);
+}
+
+void
+cpu_kstat_attach(struct cpu_info *ci)
+{
+	struct kstat *ks;
+	struct cpu_kstats *ck;
+
+	uint64_t midr, impl, part;
+	const char *impl_name = NULL, *part_name = NULL;
+	const struct cpu_cores *coreselecter = cpu_cores_none;
+	size_t i;
+
+	ks = kstat_create("mach", 0, "cpu", ci->ci_cpuid, KSTAT_T_KV, 0);
+	if (ks == NULL) {
+		printf("%s: unable to create cpu kstats\n",
+		    ci->ci_dev->dv_xname);
+		/* printf? */
+		return;
+	}
+
+	ck = malloc(sizeof(*ck), M_DEVBUF, M_WAITOK);
+
+	kstat_kv_init(&ck->ck_device, "device", KSTAT_KV_T_ISTR);
+	if (strlcpy(kstat_kv_istr(&ck->ck_device), ci->ci_dev->dv_xname,
+	    sizeof(kstat_kv_istr(&ck->ck_device))) >=
+            sizeof(kstat_kv_istr(&ck->ck_device)))
+                panic("%s: devname too long", __func__);
+
+	midr = READ_SPECIALREG(midr_el1);
+	impl = CPU_IMPL(midr);
+	part = CPU_PART(midr);
+
+	for (i = 0; cpu_implementers[i].name; i++) {
+		if (impl == cpu_implementers[i].id) {
+			impl_name = cpu_implementers[i].name;
+			coreselecter = cpu_implementers[i].corelist;
+			break;
+		}
+	}
+
+	if (impl_name) {
+		kstat_kv_init(&ck->ck_impl, "impl", KSTAT_KV_T_ISTR);
+		strlcpy(kstat_kv_istr(&ck->ck_impl), impl_name,
+		    sizeof(kstat_kv_istr(&ck->ck_impl)));
+	} else
+		kstat_kv_init(&ck->ck_impl, "impl", KSTAT_KV_T_NULL);
+
+	for (i = 0; coreselecter[i].name; i++) {
+		if (part == coreselecter[i].id) {
+			part_name = coreselecter[i].name;
+			break;
+		}
+	}
+
+	if (part_name) {
+		kstat_kv_init(&ck->ck_part, "part", KSTAT_KV_T_ISTR);
+		strlcpy(kstat_kv_istr(&ck->ck_part), part_name,
+		    sizeof(kstat_kv_istr(&ck->ck_part)));
+	} else
+		kstat_kv_init(&ck->ck_part, "part", KSTAT_KV_T_NULL);
+
+	kstat_kv_init(&ck->ck_var, "var", KSTAT_KV_T_UINT32);
+	kstat_kv_u32(&ck->ck_var) = CPU_VAR(midr);
+	kstat_kv_init(&ck->ck_rev, "rev", KSTAT_KV_T_UINT32);
+	kstat_kv_u32(&ck->ck_rev) = CPU_REV(midr);
+
+	kstat_kv_init(&ck->ck_freq, "freq", KSTAT_KV_T_UINT32);
+	kstat_kv_init(&ck->ck_mv, "mvolts?", KSTAT_KV_T_UINT32);
+
+	ks->ks_softc = ci;
+	ks->ks_data = ck;
+	ks->ks_datalen = sizeof(*ck);
+	ks->ks_read = cpu_kstat_read;
+
+	kstat_install(ks);
+
+	/* XXX should we have a ci->ci_kstat = ks? */
+}
+
+#endif /* NKSTAT > 0 */