OS-6400 want HVM exclusion lock

Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Approved by: Robert Mustacchi <rm@joyent.com>

usr/src/uts/i86pc/Makefile.files

@@ -99,6 +99,7 @@ CORE_OBJS +=			\
 	memscrub.o		\
 	mpcore.o		\
 	notes.o			\
+	pc_hvm.o		\
 	pci_bios.o		\
 	pci_cfgacc.o		\
 	pci_cfgacc_x86.o	\

usr/src/uts/i86pc/os/pc_hvm.c

@@ -0,0 +1,57 @@
+/*
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ */
+
+/*
+ * Copyright 2017 Joyent, Inc.
+ */
+
+#include <sys/param.h>
+#include <sys/types.h>
+#include <sys/mutex.h>
+#include <sys/debug.h>
+
+static kmutex_t hvm_excl_lock;
+static const char *hvm_excl_holder = NULL;
+
+/*
+ * HVM Exclusion Interface
+ *
+ * To avoid VMX/SVM conflicts from arising when multiple hypervisor providers
+ * (eg. KVM, bhyve) are shipped with the system, this simple advisory locking
+ * system is presented for their use.  Until a proper hypervisor API, like the
+ * one in OSX, is shipped in illumos, this will serve as opt-in regulation to
+ * dictate that only a single hypervisor be allowed to configure the system and
+ * run at any given time.
+ */
+
+boolean_t
+hvm_excl_hold(const char *consumer)
+{
+	boolean_t res = B_FALSE;
+
+	mutex_enter(&hvm_excl_lock);
+	if (hvm_excl_holder == NULL) {
+		hvm_excl_holder = consumer;
+		res = B_TRUE;
+	}
+	mutex_exit(&hvm_excl_lock);
+
+	return (res);
+}
+
+void
+hvm_excl_rele(const char *consumer)
+{
+	mutex_enter(&hvm_excl_lock);
+	VERIFY(consumer == hvm_excl_holder);
+	hvm_excl_holder = NULL;
+	mutex_exit(&hvm_excl_lock);
+}

usr/src/uts/i86pc/sys/pc_hvm.h

@@ -0,0 +1,35 @@
+/*
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ */
+
+/*
+ * Copyright 2017 Joyent, Inc.
+ */
+
+
+#ifndef _PC_HVM_H
+#define	_PC_HVM_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if defined(_KERNEL)
+
+extern boolean_t hvm_excl_hold(const char *);
+extern void hvm_excl_rele(const char *);
+
+#endif /* defined(_KERNEL) */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _PC_HVM_H */