From f8f1bb83f78e8a2b7f4f10432882c39bbd7952fb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= <royger@FreeBSD.org>
Date: Fri, 21 Aug 2015 15:53:08 +0000
Subject: [PATCH] xen: allow disabling PV disks and nics

Introduce two new loader tunnables that can be used to disable PV disks and
PV nics at boot time. They default to 0 and should be set to 1 (or any
number different than 0) in order to disable the PV devices:

hw.xen.disable_pv_disks=1
hw.xen.disable_pv_nics=1

In /boot/loader.conf will disable both PV disks and nics.

Sponsored by:	Citrix Systems R&D
Tested by:	Karl Pielorz <kpielorz_lst@tdx.co.uk>
MFC after:	1 week
---
 sys/dev/xen/blkfront/blkfront.c |  3 +++
 sys/dev/xen/netfront/netfront.c |  3 +++
 sys/x86/xen/hvm.c               | 28 ++++++++++++++++++++++++----
 sys/xen/xen-os.h                |  3 +++
 4 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/sys/dev/xen/blkfront/blkfront.c b/sys/dev/xen/blkfront/blkfront.c
index 5ff9d38a68dc..1416c28192ee 100644
--- a/sys/dev/xen/blkfront/blkfront.c
+++ b/sys/dev/xen/blkfront/blkfront.c
@@ -1366,6 +1366,9 @@ xbd_probe(device_t dev)
 	if (strcmp(xenbus_get_type(dev), "vbd") != 0)
 		return (ENXIO);
 
+	if (xen_hvm_domain() && xen_disable_pv_disks != 0)
+		return (ENXIO);
+
 	if (xen_hvm_domain()) {
 		int error;
 		char *type;
diff --git a/sys/dev/xen/netfront/netfront.c b/sys/dev/xen/netfront/netfront.c
index 302c0179e80c..703b44fedbb7 100644
--- a/sys/dev/xen/netfront/netfront.c
+++ b/sys/dev/xen/netfront/netfront.c
@@ -445,6 +445,9 @@ static int
 netfront_probe(device_t dev)
 {
 
+	if (xen_hvm_domain() && xen_disable_pv_nics != 0)
+		return (ENXIO);
+
 	if (!strcmp(xenbus_get_type(dev), "vif")) {
 		device_set_desc(dev, "Virtual Network Interface");
 		return (0);
diff --git a/sys/x86/xen/hvm.c b/sys/x86/xen/hvm.c
index 9ad196a83f4f..c969e262b956 100644
--- a/sys/x86/xen/hvm.c
+++ b/sys/x86/xen/hvm.c
@@ -100,8 +100,15 @@ DPCPU_DEFINE(struct vcpu_info *, vcpu_info);
 shared_info_t *HYPERVISOR_shared_info;
 start_info_t *HYPERVISOR_start_info;
 
+
+/*------------------------------ Sysctl tunables -----------------------------*/
+int xen_disable_pv_disks = 0;
+int xen_disable_pv_nics = 0;
+TUNABLE_INT("hw.xen.disable_pv_disks", &xen_disable_pv_disks);
+TUNABLE_INT("hw.xen.disable_pv_nics", &xen_disable_pv_nics);
+
 #ifdef SMP
-/* XEN diverged cpu operations */
+/*---------------------- XEN diverged cpu operations -------------------------*/
 static void
 xen_hvm_cpu_resume(void)
 {
@@ -256,21 +263,34 @@ enum {
 static void
 xen_hvm_disable_emulated_devices(void)
 {
+	u_short disable_devs = 0;
 
 	if (xen_pv_domain()) {
 		/*
 		 * No emulated devices in the PV case, so no need to unplug
 		 * anything.
 		 */
+		if (xen_disable_pv_disks != 0 || xen_disable_pv_nics != 0)
+			printf("PV devices cannot be disabled in PV guests\n");
 		return;
 	}
 
 	if (inw(XEN_MAGIC_IOPORT) != XMI_MAGIC)
 		return;
 
-	if (bootverbose)
-		printf("XEN: Disabling emulated block and network devices\n");
-	outw(XEN_MAGIC_IOPORT, XMI_UNPLUG_IDE_DISKS|XMI_UNPLUG_NICS);
+	if (xen_disable_pv_disks == 0) {
+		if (bootverbose)
+			printf("XEN: disabling emulated disks\n");
+		disable_devs |= XMI_UNPLUG_IDE_DISKS;
+	}
+	if (xen_disable_pv_nics == 0) {
+		if (bootverbose)
+			printf("XEN: disabling emulated nics\n");
+		disable_devs |= XMI_UNPLUG_NICS;
+	}
+
+	if (disable_devs != 0)
+		outw(XEN_MAGIC_IOPORT, disable_devs);
 }
 
 static void
diff --git a/sys/xen/xen-os.h b/sys/xen/xen-os.h
index 7ceef4f1c5ae..ab594d437058 100644
--- a/sys/xen/xen-os.h
+++ b/sys/xen/xen-os.h
@@ -56,6 +56,9 @@ extern start_info_t *HYPERVISOR_start_info;
 /* XXX: we need to get rid of this and use HYPERVISOR_start_info directly */
 extern char *console_page;
 
+extern int xen_disable_pv_disks;
+extern int xen_disable_pv_nics;
+
 enum xen_domain_type {
 	XEN_NATIVE,             /* running on bare hardware    */
 	XEN_PV_DOMAIN,          /* running in a PV domain      */