Add pvbus(4), a pseudo-bus to attach non-PCI paravirtual devices and buses.

vmt(4) is moved from mainbus0 to pvbus0, more devices will follow.

OK sf@ deraadt@

14 files changed, 353 insertions, 37 deletions

diff --git a/sys/arch/amd64/amd64/identcpu.c b/sys/arch/amd64/amd64/identcpu.c
index ed7dbd336d7..e074300642b 100644
--- a/sys/arch/amd64/amd64/identcpu.c
+++ b/sys/arch/amd64/amd64/identcpu.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: identcpu.c,v 1.62 2015/05/28 20:10:58 guenther Exp $	*/
+/*	$OpenBSD: identcpu.c,v 1.63 2015/07/21 03:38:22 reyk Exp $	*/
 /*	$NetBSD: identcpu.c,v 1.1 2003/04/26 18:39:28 fvdl Exp $	*/
 
 /*
@@ -56,6 +56,11 @@ int amd64_has_aesni;
 #endif
 int has_rdrand;
 
+#include "pvbus.h"
+#if NPVBUS > 0
+#include <dev/pv/pvvar.h>
+#endif
+
 const struct {
 	u_int32_t	bit;
 	char		str[12];
@@ -561,6 +566,11 @@ identifycpu(struct cpu_info *ci)
 		if (cpu_ecxfeature & CPUIDECX_RDRAND)
 			has_rdrand = 1;
 
+#if NPVBUS > 0
+		if (cpu_ecxfeature & CPUIDECX_HV)
+			has_hv_cpuid = 1;
+#endif
+
 		if (ci->ci_feature_sefflags & SEFF0EBX_SMAP)
 			replacesmap();
 	}
diff --git a/sys/arch/amd64/amd64/mainbus.c b/sys/arch/amd64/amd64/mainbus.c
index b0dc4c04da4..4bfb0601f4d 100644
--- a/sys/arch/amd64/amd64/mainbus.c
+++ b/sys/arch/amd64/amd64/mainbus.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mainbus.c,v 1.28 2015/03/14 03:38:46 jsg Exp $	*/
+/*	$OpenBSD: mainbus.c,v 1.29 2015/07/21 03:38:22 reyk Exp $	*/
 /*	$NetBSD: mainbus.c,v 1.1 2003/04/26 18:39:29 fvdl Exp $	*/
 
 /*
@@ -48,7 +48,7 @@
 #include "ipmi.h"
 #include "bios.h"
 #include "mpbios.h"
-#include "vmt.h"
+#include "pvbus.h"
 
 #include <machine/cpuvar.h>
 #include <machine/i82093var.h>
@@ -59,8 +59,8 @@
 #include <dev/ipmivar.h>
 #endif
 
-#if NVMT > 0
-#include <dev/vmtvar.h>
+#if NPVBUS > 0
+#include <dev/pv/pvvar.h>
 #endif
 
 #if NBIOS > 0
@@ -92,6 +92,9 @@ union mainbus_attach_args {
 #if NBIOS > 0
 	struct bios_attach_args mba_bios;
 #endif
+#if NPVBUS > 0
+	struct pvbus_attach_args mba_pvba;
+#endif
 };
 
 /*
@@ -170,10 +173,11 @@ mainbus_attach(struct device *parent, struct device *self, void *aux)
 	}
 #endif
 
-#if NVMT > 0
-	if (vmt_probe()) {
-		mba.mba_busname = "vmt";
-		config_found(self, &mba.mba_busname, mainbus_print);
+#if NPVBUS > 0
+	/* Probe first to hide the "not configured" message */
+	if (pvbus_probe()) {
+		mba.mba_pvba.pvba_busname = "pvbus";
+		config_found(self, &mba.mba_pvba.pvba_busname, mainbus_print);
 	}
 #endif
 
diff --git a/sys/arch/amd64/conf/GENERIC b/sys/arch/amd64/conf/GENERIC
index cb96cf9aa6d..33e8361c22d 100644
--- a/sys/arch/amd64/conf/GENERIC
+++ b/sys/arch/amd64/conf/GENERIC
@@ -1,4 +1,4 @@
-#	$OpenBSD: GENERIC,v 1.390 2015/07/19 18:17:06 bmercer Exp $
+#	$OpenBSD: GENERIC,v 1.391 2015/07/21 03:38:22 reyk Exp $
 #
 # For further information on compiling OpenBSD kernels, see the config(8)
 # man page.
@@ -38,6 +38,7 @@ isa0	at pcib?
 isa0	at amdpcib?
 isa0	at tcpcib?
 pci*	at mainbus0
+pvbus0	at mainbus0
 
 acpi0		at bios0
 acpitimer*	at acpi?
@@ -64,7 +65,8 @@ aibs*		at acpi?
 mpbios0		at bios0
 
 ipmi0	at mainbus? disable	# IPMI
-vmt0	at mainbus?		# VMware Tools
+
+vmt0	at pvbus?		# VMware Tools
 
 option		PCIVERBOSE
 option		USBVERBOSE
diff --git a/sys/arch/amd64/conf/files.amd64 b/sys/arch/amd64/conf/files.amd64
index 270dffd2cb7..57942f9410c 100644
--- a/sys/arch/amd64/conf/files.amd64
+++ b/sys/arch/amd64/conf/files.amd64
@@ -1,4 +1,4 @@
-#	$OpenBSD: files.amd64,v 1.78 2015/07/17 22:52:28 tedu Exp $
+#	$OpenBSD: files.amd64,v 1.79 2015/07/21 03:38:22 reyk Exp $
 
 maxpartitions 16
 maxusers 2 16 128
@@ -234,8 +234,10 @@ include "dev/onewire/files.onewire"
 #
 attach	ipmi at mainbus
 
-# VMware Tools
-attach	vmt at mainbus
+#
+# Paravirtual device bus
+#
+include "dev/pv/files.pv"
 
 #
 # device major numbers
diff --git a/sys/arch/i386/conf/GENERIC b/sys/arch/i386/conf/GENERIC
index 13767a85c8f..a2378e6fc4d 100644
--- a/sys/arch/i386/conf/GENERIC
+++ b/sys/arch/i386/conf/GENERIC
@@ -1,4 +1,4 @@
-#	$OpenBSD: GENERIC,v 1.800 2015/07/19 18:17:06 bmercer Exp $
+#	$OpenBSD: GENERIC,v 1.801 2015/07/21 03:38:22 reyk Exp $
 #
 # For further information on compiling OpenBSD kernels, see the config(8)
 # man page.
@@ -42,10 +42,12 @@ acpi0	at bios?
 mpbios0	at bios0
 pcibios0 at bios0 flags 0x0000	# use 0x30 for a total verbose
 ipmi0	at mainbus? disable	# IPMI
-vmt0	at mainbus?		# VMware Tools
 esm0	at mainbus? 		# Dell Embedded Server Management
 amdmsr0	at mainbus?		# MSR access for AMD Geode LX CPUs with GP
 
+pvbus0	at mainbus0		# Paravirtual device bus
+vmt0	at pvbus?		# VMware Tools
+
 acpitimer*	at acpi?
 acpihpet*	at acpi?
 acpiac*		at acpi?
diff --git a/sys/arch/i386/conf/files.i386 b/sys/arch/i386/conf/files.i386
index a1b2c3b8b1c..25e96b1cbfe 100644
--- a/sys/arch/i386/conf/files.i386
+++ b/sys/arch/i386/conf/files.i386
@@ -1,4 +1,4 @@
-#	$OpenBSD: files.i386,v 1.224 2015/07/17 22:52:28 tedu Exp $
+#	$OpenBSD: files.i386,v 1.225 2015/07/21 03:38:22 reyk Exp $
 #
 # new style config file for i386 architecture
 #
@@ -392,8 +392,10 @@ file	arch/i386/i386/acpi_wakecode.S		acpi & !small_kernel
 #
 attach	ipmi at mainbus
 
-# VMware Tools
-attach	vmt at mainbus
+#
+# Paravirtual device bus
+#
+include "dev/pv/files.pv"
 
 # Dell Embedded Systems Management
 device	esm
diff --git a/sys/arch/i386/i386/machdep.c b/sys/arch/i386/i386/machdep.c
index 959832f4dc0..1dc4a2637fc 100644
--- a/sys/arch/i386/i386/machdep.c
+++ b/sys/arch/i386/i386/machdep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: machdep.c,v 1.573 2015/07/16 23:03:40 sf Exp $	*/
+/*	$OpenBSD: machdep.c,v 1.574 2015/07/21 03:38:22 reyk Exp $	*/
 /*	$NetBSD: machdep.c,v 1.214 1996/11/10 03:16:17 thorpej Exp $	*/
 
 /*-
@@ -316,6 +316,11 @@ int allowaperture = 0;
 
 int has_rdrand;
 
+#include "pvbus.h"
+#if NPVBUS > 0
+#include <dev/pv/pvvar.h>
+#endif
+
 void	winchip_cpu_setup(struct cpu_info *);
 void	amd_family5_setperf_setup(struct cpu_info *);
 void	amd_family5_setup(struct cpu_info *);
@@ -2011,6 +2016,11 @@ identifycpu(struct cpu_info *ci)
 		if (ci->ci_feature_sefflags & SEFF0EBX_SMAP)
 			replacesmap();
 #endif
+
+#if NPVBUS > 0
+		if (cpu_ecxfeature & CPUIDECX_HV)
+			has_hv_cpuid = 1;
+#endif
 	}
 
 #ifndef SMALL_KERNEL
diff --git a/sys/arch/i386/i386/mainbus.c b/sys/arch/i386/i386/mainbus.c
index 1af1664aa48..9a471600571 100644
--- a/sys/arch/i386/i386/mainbus.c
+++ b/sys/arch/i386/i386/mainbus.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mainbus.c,v 1.50 2012/10/04 08:32:20 ehrhardt Exp $	*/
+/*	$OpenBSD: mainbus.c,v 1.51 2015/07/21 03:38:22 reyk Exp $	*/
 /*	$NetBSD: mainbus.c,v 1.21 1997/06/06 23:14:20 thorpej Exp $	*/
 
 /*
@@ -52,9 +52,9 @@
 #include "acpi.h"
 #include "ipmi.h"
 #include "esm.h"
-#include "vmt.h"
 #include "vesabios.h"
 #include "amdmsr.h"
+#include "pvbus.h"
 
 #include <machine/cpuvar.h>
 #include <machine/i82093var.h>
@@ -69,8 +69,8 @@
 #include <dev/ipmivar.h>
 #endif
 
-#if NVMT > 0
-#include <dev/vmtvar.h>
+#if NPVBUS > 0
+#include <dev/pv/pvvar.h>
 #endif
 
 #if NAMDMSR > 0
@@ -115,6 +115,9 @@ union mainbus_attach_args {
 #if NESM > 0
 	struct esm_attach_args mba_eaa;
 #endif
+#if NPVBUS > 0
+	struct pvbus_attach_args mba_pvba;
+#endif
 };
 
 /*
@@ -164,10 +167,11 @@ mainbus_attach(struct device *parent, struct device *self, void *aux)
 	}
 #endif
 
-#if NVMT > 0
-	if (vmt_probe()) {
-		mba.mba_busname = "vmt";
-		config_found(self, &mba.mba_busname, mainbus_print);
+#if NPVBUS > 0
+	/* Probe first to hide the "not configured" message */
+	if (pvbus_probe()) {
+		mba.mba_pvba.pvba_busname = "pvbus";
+		config_found(self, &mba.mba_pvba.pvba_busname, mainbus_print);
 	}
 #endif
 
diff --git a/sys/conf/files b/sys/conf/files
index b1ae3a5a8df..82972b6e122 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -1,4 +1,4 @@
-#	$OpenBSD: files,v 1.598 2015/07/20 22:16:41 rzalamena Exp $
+#	$OpenBSD: files,v 1.599 2015/07/21 03:38:22 reyk Exp $
 #	$NetBSD: files,v 1.87 1996/05/19 17:17:50 jonathan Exp $
 
 #	@(#)files.newconf	7.5 (Berkeley) 5/10/93
@@ -486,10 +486,6 @@ file dev/radio.c			radio	needs-flag
 device	ipmi
 file	dev/ipmi.c			ipmi	needs-flag
 
-# VMware Tools
-device	vmt
-file	dev/vmt.c			vmt	needs-flag
-
 # Virtual SCSI
 device	vscsi: scsi
 attach	vscsi at root
diff --git a/sys/dev/pv/files.pv b/sys/dev/pv/files.pv
new file mode 100644
index 00000000000..d0834032390
--- /dev/null
+++ b/sys/dev/pv/files.pv
@@ -0,0 +1,14 @@
+#	$OpenBSD: files.pv,v 1.1 2015/07/21 03:38:22 reyk Exp $
+#
+# Config file and device description for paravirtual devices.
+# Included by ports that need it.
+
+define	pvbus {}
+device	pvbus
+attach	pvbus at mainbus
+file	dev/pv/pvbus.c			pvbus	needs-flag
+
+# VMware Tools
+device	vmt
+attach	vmt at pvbus
+file	dev/vmt.c			vmt	needs-flag
diff --git a/sys/dev/pv/pvbus.c b/sys/dev/pv/pvbus.c
new file mode 100644
index 00000000000..bc886f0814f
--- /dev/null
+++ b/sys/dev/pv/pvbus.c
@@ -0,0 +1,193 @@
+/*	$OpenBSD: pvbus.c,v 1.1 2015/07/21 03:38:22 reyk Exp $	*/
+
+/*
+ * Copyright (c) 2015 Reyk Floeter <reyk@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#if !defined(__i386__) && !defined(__amd64__)
+#error pvbus(4) is currently only supported on i386 and amd64
+#endif
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/timeout.h>
+#include <sys/signalvar.h>
+#include <sys/syslog.h>
+#include <sys/proc.h>
+#include <sys/socket.h>
+
+#include <machine/specialreg.h>
+
+#include <dev/rndvar.h>
+
+#include <dev/pv/pvvar.h>
+#include <dev/pv/pvreg.h>
+
+#include "vmt.h"
+
+int has_hv_cpuid = 0;
+
+extern void rdrand(void *);
+
+int	 pvbus_activate(struct device *, int);
+int	 pvbus_match(struct device *, void *, void *);
+void	 pvbus_attach(struct device *, struct device *, void *);
+int	 pvbus_print(void *, const char *);
+
+struct cfattach pvbus_ca = {
+	sizeof(struct pvbus_softc),
+	pvbus_match,
+	pvbus_attach,
+	NULL,
+	pvbus_activate
+};
+
+struct cfdriver pvbus_cd = {
+	NULL,
+	"pvbus",
+	DV_DULL
+};
+
+struct pvbus_type {
+	const char	*signature;
+	const char	*name;
+	unsigned int	 type;
+} pvbus_types[] = {
+	{ "KVMKVMKVM\0\0\0",	"KVM",		PVBUS_KVM },
+	{ "Microsoft Hv",	"Hyper-V",	PVBUS_HYPERV },
+	{ "VMwareVMware",	"VMware",	PVBUS_VMWARE },
+	{ "XenVMMXenVMM",	"Xen",		PVBUS_XEN },
+	{ NULL }
+};
+
+struct pv_attach_args pvbus_devices[] = {
+#if NVMT > 0
+	{ "vmt",	PVBUS_VMWARE	},
+#endif
+	{ NULL }
+};
+
+int
+pvbus_probe(void)
+{
+	/* Must be set in identcpu */
+	if (!has_hv_cpuid)
+		return (0);
+	return (1);
+}
+
+int
+pvbus_match(struct device *parent, void *match, void *aux)
+{
+	const char **busname = (const char **)aux;
+	return (strcmp(*busname, pvbus_cd.cd_name) == 0);
+}
+
+void
+pvbus_attach(struct device *parent, struct device *self, void *aux)
+{
+	struct pvbus_softc *sc = (struct pvbus_softc *)self;
+	struct pv_attach_args *pva;
+	uint32_t reg0, base;
+	union {
+		uint32_t	regs[3];
+		char		str[CPUID_HV_SIGNATURE_STRLEN];
+	} r;
+	int i;
+
+	printf(":");
+
+	for (base = CPUID_HV_SIGNATURE_START;
+	    base < CPUID_HV_SIGNATURE_END;
+	    base += CPUID_HV_SIGNATURE_STEP) {
+		CPUID(base, reg0, r.regs[0], r.regs[1], r.regs[2]);
+		for (i = 0; i < 4; i++) {
+			/*
+			 * Check if first 4 chars are printable ASCII as
+			 * minimal validity check
+			 */
+			if (r.str[i] < 32 || r.str[i] > 126)
+				goto out;
+		}
+
+		for (i = 0; pvbus_types[i].signature != NULL; i++) {
+			if (memcmp(pvbus_types[i].signature, r.str,
+			    CPUID_HV_SIGNATURE_STRLEN) != 0)
+				continue;
+			sc->pvbus_types |= pvbus_types[i].type;
+
+			printf(" %s", pvbus_types[i].name);
+		}
+	}
+
+ out:
+	printf("\n");
+
+#ifdef notyet
+	/* XXX get hypervisor-specific features */
+	if (sc->pvbus_types & PVBUS_KVM) {
+		kvm_cpuid_base = base;
+		CPUID(base + CPUID_OFFSET_KVM_FEATURES,
+		    reg0, r.regs[0], r.regs[1], r.regs[2]);
+		kvm_features = reg0;
+	}
+	if (sc->pvbus_types & PVBUS_HYPERV) {
+		/* XXX */
+	}
+#endif
+
+	/* Attach drivers */
+	for (i = 0; pvbus_devices[i].pva_busname != NULL; i++) {
+		pva = &pvbus_devices[i];
+		pva->pva_types = sc->pvbus_types;
+		if (sc->pvbus_types & pva->pva_type)
+			config_found(self, &pva->pva_busname,
+			    pvbus_print);
+	}
+}
+
+int
+pvbus_activate(struct device *self, int act)
+{
+	int rv = 0;
+
+	switch (act) {
+	case DVACT_SUSPEND:
+		rv = config_activate_children(self, act);
+		break;
+	case DVACT_RESUME:
+		rv = config_activate_children(self, act);
+		break;
+	case DVACT_POWERDOWN:
+		rv = config_activate_children(self, act);
+		break;
+	default:
+		rv = config_activate_children(self, act);
+		break;
+	}
+
+	return (rv);
+}
+
+int
+pvbus_print(void *aux, const char *pnp)
+{
+	struct pv_attach_args	*pva = aux;
+	if (pnp)
+		printf("%s at %s", pva->pva_busname, pnp);
+	return (UNCONF);
+}
diff --git a/sys/dev/pv/pvreg.h b/sys/dev/pv/pvreg.h
new file mode 100644
index 00000000000..1fa19dee558
--- /dev/null
+++ b/sys/dev/pv/pvreg.h
@@ -0,0 +1,45 @@
+/*	$OpenBSD: pvreg.h,v 1.1 2015/07/21 03:38:22 reyk Exp $	*/
+
+/*
+ * Copyright (c) 2015 Reyk Floeter <reyk@openbsd.org>
+ * Copyright (c) 2015 Stefan Fritsch <sf@sfritsch.de>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef _DEV_PV_PVBUS_H_
+#define _DEV_PV_PVBUS_H_
+
+#define	CPUID_HV_SIGNATURE_START	0x40000000
+#define	CPUID_HV_SIGNATURE_END		0x40010000
+#define	CPUID_HV_SIGNATURE_STEP		0x100
+#define CPUID_HV_SIGNATURE_STRLEN	12
+
+/* KVM */
+#define	CPUID_OFFSET_KVM_FEATURES		0x1
+
+#define	KVM_FEATURE_CLOCKSOURCE			0	/* deprecated */
+#define	KVM_FEATURE_NOP_IO_DELAY		1
+#define	KVM_FEATURE_MMU_OP			2	/* deprecated */
+#define	KVM_FEATURE_CLOCKSOURCE2		3
+#define	KVM_FEATURE_ASYNC_PF			4
+#define	KVM_FEATURE_STEAL_TIME			5
+#define	KVM_FEATURE_PV_EOI			6
+#define	KVM_FEATURE_PV_UNHALT			7
+#define	KVM_FEATURE_CLOCKSOURCE_STABLE_BIT	24
+
+#define	MSR_KVM_EOI_EN				0x4b564d04
+
+#define KVM_PV_EOI_BIT				0
+
+#endif /* _DEV_PV_PVBUS_H_ */
diff --git a/sys/dev/vmtvar.h b/sys/dev/pv/pvvar.h
index 5029d5e6085..06161c7d51a 100644
--- a/sys/dev/vmtvar.h
+++ b/sys/dev/pv/pvvar.h
@@ -1,7 +1,7 @@
-/*	$OpenBSD: vmtvar.h,v 1.1 2008/07/08 05:22:00 dlg Exp $ */
+/*	$OpenBSD: pvvar.h,v 1.1 2015/07/21 03:38:22 reyk Exp $	*/
 
 /*
- * Copyright (c) 2008 David Gwynne <dlg@openbsd.org>
+ * Copyright (c) 2015 Reyk Floeter <reyk@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -16,4 +16,31 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-int	vmt_probe(void);
+#ifndef _DEV_PV_PVVAR_H_
+#define _DEV_PV_PVVAR_H_
+
+struct pvbus_softc {
+	struct device		 pvbus_dev;
+	uint8_t			 pvbus_types;
+};
+
+struct pvbus_attach_args {
+	const char		*pvba_busname;
+};
+
+struct pv_attach_args {
+	const char		*pva_busname;
+	uint8_t			 pva_type;	/* required hv type */
+	uint8_t			 pva_types;	/* detected hv types */
+};
+
+extern int has_hv_cpuid;
+
+#define PVBUS_KVM	0x01
+#define PVBUS_HYPERV	0x02
+#define PVBUS_VMWARE	0x04
+#define PVBUS_XEN	0x08
+
+int	 pvbus_probe(void);
+
+#endif /* _DEV_PV_PVBUS_H_ */
diff --git a/sys/dev/vmt.c b/sys/dev/vmt.c
index d21ec59e96d..b1b02c457bf 100644
--- a/sys/dev/vmt.c
+++ b/sys/dev/vmt.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vmt.c,v 1.29 2015/03/14 03:38:46 jsg Exp $ */
+/*	$OpenBSD: vmt.c,v 1.30 2015/07/21 03:38:22 reyk Exp $ */
 
 /*
  * Copyright (c) 2007 David Crawshaw <david@zentus.com>
@@ -226,6 +226,8 @@ void	 vmt_tclo_resume(struct vmt_softc *);
 void	 vmt_tclo_capreg(struct vmt_softc *);
 void	 vmt_tclo_broadcastip(struct vmt_softc *);
 
+int	 vmt_probe(void);
+
 struct vmt_tclo_rpc {
 	const char	*name;
 	void		(*cb)(struct vmt_softc *);
@@ -317,6 +319,9 @@ vmt_match(struct device *parent, void *match, void *aux)
 {
 	const char **busname = (const char **)aux;
 
+	if (!vmt_probe())
+		return (0);
+
 	return (strcmp(*busname, vmt_cd.cd_name) == 0);
 }