diff --git a/lib/libpmc/libpmc.c b/lib/libpmc/libpmc.c
--- a/lib/libpmc/libpmc.c
+++ b/lib/libpmc/libpmc.c
@@ -33,7 +33,6 @@
 #include <sys/pmc.h>
 #include <sys/syscall.h>
 
-#include <assert.h>
 #include <ctype.h>
 #include <errno.h>
 #include <err.h>
@@ -1083,14 +1082,8 @@
 	r = spec_copy = strdup(ctrspec);
 	ctrname = strsep(&r, ",");
 	if (pmc_pmu_enabled()) {
-		if (pmc_pmu_pmcallocate(ctrname, &pmc_config) == 0) {
-			/*
-			 * XXX: pmclog_get_event exploits this to disambiguate
-			 *      PMU from PMC event codes in PMCALLOCATE events.
-			 */
-			assert(pmc_config.pm_ev < PMC_EVENT_FIRST);
+		if (pmc_pmu_pmcallocate(ctrname, &pmc_config) == 0)
 			goto found;
-		}
 	}
 	free(spec_copy);
 	spec_copy = NULL;
diff --git a/lib/libpmc/libpmc_pmu_util.c b/lib/libpmc/libpmc_pmu_util.c
--- a/lib/libpmc/libpmc_pmu_util.c
+++ b/lib/libpmc/libpmc_pmu_util.c
@@ -649,7 +649,6 @@
 	assert(idx >= 0);
 	pm->pm_ev = idx;
 	pm->pm_md.pm_md_config = ped.ped_event;
-	pm->pm_md.pm_md_flags |= PM_MD_RAW_EVENT;
 	pm->pm_class = PMC_CLASS_ARMV8;
 	pm->pm_caps |= (PMC_CAP_READ | PMC_CAP_WRITE);
 
@@ -680,5 +679,6 @@
 		return (error);
 	}
 
+	pm->pm_flags |= PMC_F_EV_PMU;
 	return (0);
 }
diff --git a/lib/libpmc/pmclog.c b/lib/libpmc/pmclog.c
--- a/lib/libpmc/pmclog.c
+++ b/lib/libpmc/pmclog.c
@@ -357,15 +357,10 @@
 		PMCLOG_READ64(le,ev->pl_u.pl_a.pl_rate);
 
 		/*
-		 * Could be either a PMC event code or a PMU event index;
-		 * assume that their encodings don't overlap (i.e. no PMU event
-		 * table is more than 0x1000 entries) to distinguish them here.
-		 * Otherwise pmc_pmu_event_get_by_idx will go out of bounds if
-		 * given a PMC event code when it knows about that CPU.
-		 *
-		 * XXX: Ideally we'd have user flags to give us that context.
+		 * pl_event could contain either a PMC event code or a PMU
+		 * event index.
 		 */
-		if (ev->pl_u.pl_a.pl_event < PMC_EVENT_FIRST)
+		if ((ev->pl_u.pl_a.pl_flags & PMC_F_EV_PMU) != 0)
 			ev->pl_u.pl_a.pl_evname =
 			    pmc_pmu_event_get_by_idx(ps->ps_cpuid,
 				ev->pl_u.pl_a.pl_event);
diff --git a/sys/arm64/include/pmc_mdep.h b/sys/arm64/include/pmc_mdep.h
--- a/sys/arm64/include/pmc_mdep.h
+++ b/sys/arm64/include/pmc_mdep.h
@@ -45,8 +45,6 @@
 union pmc_md_op_pmcallocate {
 	struct {
 		uint32_t	pm_md_config;
-		uint32_t	pm_md_flags;
-#define	PM_MD_RAW_EVENT		0x1
 	};
 	struct pmc_md_cmn600_pmu_op_pmcallocate	pm_cmn600;
 	struct pmc_md_dmc620_pmu_op_pmcallocate	pm_dmc620;
diff --git a/sys/dev/hwpmc/hwpmc_amd.c b/sys/dev/hwpmc/hwpmc_amd.c
--- a/sys/dev/hwpmc/hwpmc_amd.c
+++ b/sys/dev/hwpmc/hwpmc_amd.c
@@ -582,6 +582,9 @@
 	if (pd->pd_class != a->pm_class)
 		return EINVAL;
 
+	if ((a->pm_flags & PMC_F_EV_PMU) == 0)
+		return (EINVAL);
+
 	caps = pm->pm_caps;
 
 	PMCDBG2(MDP,ALL,1,"amd-allocate ri=%d caps=0x%x", ri, caps);
diff --git a/sys/dev/hwpmc/hwpmc_arm64.c b/sys/dev/hwpmc/hwpmc_arm64.c
--- a/sys/dev/hwpmc/hwpmc_arm64.c
+++ b/sys/dev/hwpmc/hwpmc_arm64.c
@@ -177,9 +177,9 @@
 	}
 	pe = a->pm_ev;
 
-	/* Adjust the config value if needed. */
-	config = a->pm_md.pm_md_config;
-	if ((a->pm_md.pm_md_flags & PM_MD_RAW_EVENT) == 0) {
+	if ((a->pm_flags & PMC_F_EV_PMU) != 0) {
+		config = a->pm_md.pm_md_config;
+	} else {
 		config = (uint32_t)pe - PMC_EV_ARMV8_FIRST;
 		if (config > (PMC_EV_ARMV8_LAST - PMC_EV_ARMV8_FIRST))
 			return (EINVAL);
diff --git a/sys/dev/hwpmc/hwpmc_core.c b/sys/dev/hwpmc/hwpmc_core.c
--- a/sys/dev/hwpmc/hwpmc_core.c
+++ b/sys/dev/hwpmc/hwpmc_core.c
@@ -239,6 +239,9 @@
 	if (a->pm_class != PMC_CLASS_IAF)
 		return (EINVAL);
 
+	if ((a->pm_flags & PMC_F_EV_PMU) == 0)
+		return (EINVAL);
+
 	iap = &a->pm_md.pm_iap;
 	config = iap->pm_iap_config;
 	ev = IAP_EVSEL_GET(config);
@@ -721,6 +724,9 @@
 	if (a->pm_class != PMC_CLASS_IAP)
 		return (EINVAL);
 
+	if ((a->pm_flags & PMC_F_EV_PMU) == 0)
+		return (EINVAL);
+
 	iap = &a->pm_md.pm_iap;
 	ev = IAP_EVSEL_GET(iap->pm_iap_config);
 
diff --git a/sys/dev/hwpmc/hwpmc_mod.c b/sys/dev/hwpmc/hwpmc_mod.c
--- a/sys/dev/hwpmc/hwpmc_mod.c
+++ b/sys/dev/hwpmc/hwpmc_mod.c
@@ -3349,7 +3349,8 @@
 	 * Look for valid values for 'pm_flags'.
 	 */
 	if ((flags & ~(PMC_F_DESCENDANTS | PMC_F_LOG_PROCCSW |
-	    PMC_F_LOG_PROCEXIT | PMC_F_CALLCHAIN | PMC_F_USERCALLCHAIN)) != 0)
+	    PMC_F_LOG_PROCEXIT | PMC_F_CALLCHAIN | PMC_F_USERCALLCHAIN |
+	    PMC_F_EV_PMU)) != 0)
 		return (EINVAL);
 
 	/* PMC_F_USERCALLCHAIN is only valid with PMC_F_CALLCHAIN. */
diff --git a/sys/dev/hwpmc/hwpmc_power8.c b/sys/dev/hwpmc/hwpmc_power8.c
--- a/sys/dev/hwpmc/hwpmc_power8.c
+++ b/sys/dev/hwpmc/hwpmc_power8.c
@@ -168,6 +168,9 @@
 	if (a->pm_class != PMC_CLASS_POWER8)
 		return (EINVAL);
 
+	if ((a->pm_flags & PMC_F_EV_PMU) == 0)
+		return (EINVAL);
+
 	/*
 	 * PMC5 and PMC6 are not programmable and always count instructions
 	 * completed and cycles, respectively.
diff --git a/sys/dev/hwpmc/hwpmc_uncore.c b/sys/dev/hwpmc/hwpmc_uncore.c
--- a/sys/dev/hwpmc/hwpmc_uncore.c
+++ b/sys/dev/hwpmc/hwpmc_uncore.c
@@ -199,6 +199,9 @@
 	if (a->pm_class != PMC_CLASS_UCF)
 		return (EINVAL);
 
+	if ((a->pm_flags & PMC_F_EV_PMU) == 0)
+		return (EINVAL);
+
 	flags = UCF_EN;
 
 	pm->pm_md.pm_ucf.pm_ucf_ctrl = (flags << (ri * 4));
@@ -498,6 +501,9 @@
 	if (a->pm_class != PMC_CLASS_UCP)
 		return (EINVAL);
 
+	if ((a->pm_flags & PMC_F_EV_PMU) == 0)
+		return (EINVAL);
+
 	ucp = &a->pm_md.pm_ucp;
 	ev = UCP_EVSEL(ucp->pm_ucp_config);
 	switch (uncore_cputype) {
diff --git a/sys/sys/pmc.h b/sys/sys/pmc.h
--- a/sys/sys/pmc.h
+++ b/sys/sys/pmc.h
@@ -369,6 +369,14 @@
 #define	PMC_F_CALLCHAIN		0x00000080 /*OP ALLOCATE capture callchains */
 #define	PMC_F_USERCALLCHAIN	0x00000100 /*OP ALLOCATE use userspace stack */
 
+/* V10 API */
+#define	PMC_F_EV_PMU		0x00000200 /*
+					    * OP ALLOCATE: pm_ev has special
+					    * userspace meaning; counter
+					    * configuration is communicated
+					    * through class-dependent fields
+					    */
+
 /* internal flags */
 #define	PMC_F_ATTACHED_TO_OWNER	0x00010000 /*attached to owner*/
 #define	PMC_F_NEEDS_LOGFILE	0x00020000 /*needs log file */