MFC 304858,305485,305497: Fix various issues with PCI pass through and VT-d.

304858:
Enable I/O MMU when PCI pass through is first used.

Rather than enabling the I/O MMU when the vmm module is loaded,
defer initialization until the first attempt to pass a PCI device
through to a guest.  If the I/O MMU fails to initialize or is not
present, than fail the attempt to pass a PCI device through to a
guest.

The hw.vmm.force_iommu tunable has been removed since the I/O MMU is
no longer enabled during boot.  However, the I/O MMU support can be
disabled by setting the hw.vmm.iommu.enable tunable to 0 to prevent
use of the I/O MMU on any systems where it is buggy.

305485:
Leave ppt devices in the host domain when they are not attached to a VM.

This allows a pass through device to be reset to a normal device driver
on the host and reused on the host.  ppt devices are now always active in
some I/O MMU domain when the I/O MMU is active, either the host domain
or the domain of a VM they are attached to.

305497:
Update the I/O MMU in bhyve when PCI devices are added and removed.

When the I/O MMU is active in bhyve, all PCI devices need valid entries
in the DMAR context tables. The I/O MMU code does a single enumeration
of the available PCI devices during initialization to add all existing
devices to a domain representing the host. The ppt(4) driver then moves
pass through devices in and out of domains for virtual machines as needed.
However, when new PCI devices were added at runtime either via SR-IOV or
HotPlug, the I/O MMU tables were not updated.

This change adds a new set of EVENTHANDLERS that are invoked when PCI
devices are added and deleted. The I/O MMU driver in bhyve installs
handlers for these events which it uses to add and remove devices to
the "host" domain.

Sponsored by:	Chelsio Communications

3 files changed, 57 insertions, 12 deletions

diff --git a/sys/amd64/vmm/io/iommu.c b/sys/amd64/vmm/io/iommu.c
index 9cfc4c2..75cf1ec 100644
--- a/sys/amd64/vmm/io/iommu.c
+++ b/sys/amd64/vmm/io/iommu.c
@@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
 #include <dev/pci/pcivar.h>
 #include <dev/pci/pcireg.h>
 
+#include <machine/cpu.h>
 #include <machine/md_var.h>
 
 #include "vmm_util.h"
@@ -51,8 +52,13 @@ static int iommu_avail;
 SYSCTL_INT(_hw_vmm_iommu, OID_AUTO, initialized, CTLFLAG_RD, &iommu_avail,
     0, "bhyve iommu initialized?");
 
+static int iommu_enable = 1;
+SYSCTL_INT(_hw_vmm_iommu, OID_AUTO, enable, CTLFLAG_RDTUN, &iommu_enable, 0,
+    "Enable use of I/O MMU (required for PCI passthrough).");
+
 static struct iommu_ops *ops;
 static void *host_domain;
+static eventhandler_tag add_tag, delete_tag;
 
 static __inline int
 IOMMU_INIT(void)
@@ -148,14 +154,31 @@ IOMMU_DISABLE(void)
 		(*ops->disable)();
 }
 
-void
+static void
+iommu_pci_add(void *arg, device_t dev)
+{
+
+	/* Add new devices to the host domain. */
+	iommu_add_device(host_domain, pci_get_rid(dev));
+}
+
+static void
+iommu_pci_delete(void *arg, device_t dev)
+{
+
+	iommu_remove_device(host_domain, pci_get_rid(dev));
+}
+
+static void
 iommu_init(void)
 {
 	int error, bus, slot, func;
 	vm_paddr_t maxaddr;
-	const char *name;
 	device_t dev;
 
+	if (!iommu_enable)
+		return;
+
 	if (vmm_is_intel())
 		ops = &iommu_ops_intel;
 	else if (vmm_is_amd())
@@ -174,8 +197,13 @@ iommu_init(void)
 	 */
 	maxaddr = vmm_mem_maxaddr();
 	host_domain = IOMMU_CREATE_DOMAIN(maxaddr);
-	if (host_domain == NULL)
-		panic("iommu_init: unable to create a host domain");
+	if (host_domain == NULL) {
+		printf("iommu_init: unable to create a host domain");
+		IOMMU_CLEANUP();
+		ops = NULL;
+		iommu_avail = 0;
+		return;
+	}
 
 	/*
 	 * Create 1:1 mappings from '0' to 'maxaddr' for devices assigned to
@@ -183,6 +211,9 @@ iommu_init(void)
 	 */
 	iommu_create_mapping(host_domain, 0, 0, maxaddr);
 
+	add_tag = EVENTHANDLER_REGISTER(pci_add_device, iommu_pci_add, NULL, 0);
+	delete_tag = EVENTHANDLER_REGISTER(pci_delete_device, iommu_pci_delete,
+	    NULL, 0);
 	for (bus = 0; bus <= PCI_BUSMAX; bus++) {
 		for (slot = 0; slot <= PCI_SLOTMAX; slot++) {
 			for (func = 0; func <= PCI_FUNCMAX; func++) {
@@ -190,12 +221,7 @@ iommu_init(void)
 				if (dev == NULL)
 					continue;
 
-				/* skip passthrough devices */
-				name = device_get_name(dev);
-				if (name != NULL && strcmp(name, "ppt") == 0)
-					continue;
-
-				/* everything else belongs to the host domain */
+				/* Everything belongs to the host domain. */
 				iommu_add_device(host_domain,
 				    pci_get_rid(dev));
 			}
@@ -208,6 +234,15 @@ iommu_init(void)
 void
 iommu_cleanup(void)
 {
+
+	if (add_tag != NULL) {
+		EVENTHANDLER_DEREGISTER(pci_add_device, add_tag);
+		add_tag = NULL;
+	}
+	if (delete_tag != NULL) {
+		EVENTHANDLER_DEREGISTER(pci_delete_device, delete_tag);
+		delete_tag = NULL;
+	}
 	IOMMU_DISABLE();
 	IOMMU_DESTROY_DOMAIN(host_domain);
 	IOMMU_CLEANUP();
@@ -216,7 +251,16 @@ iommu_cleanup(void)
 void *
 iommu_create_domain(vm_paddr_t maxaddr)
 {
-
+	static volatile int iommu_initted;
+
+	if (iommu_initted < 2) {
+		if (atomic_cmpset_int(&iommu_initted, 0, 1)) {
+			iommu_init();
+			atomic_store_rel_int(&iommu_initted, 2);
+		} else
+			while (iommu_initted == 1)
+				cpu_spinwait();
+	}
 	return (IOMMU_CREATE_DOMAIN(maxaddr));
 }
 
diff --git a/sys/amd64/vmm/io/iommu.h b/sys/amd64/vmm/io/iommu.h
index 36b44fa..a941c77 100644
--- a/sys/amd64/vmm/io/iommu.h
+++ b/sys/amd64/vmm/io/iommu.h
@@ -61,7 +61,6 @@ struct iommu_ops {
 extern struct iommu_ops iommu_ops_intel;
 extern struct iommu_ops iommu_ops_amd;
 
-void	iommu_init(void);
 void	iommu_cleanup(void);
 void	*iommu_host_domain(void);
 void	*iommu_create_domain(vm_paddr_t maxaddr);
diff --git a/sys/amd64/vmm/io/ppt.c b/sys/amd64/vmm/io/ppt.c
index 692190a..6541d7d 100644
--- a/sys/amd64/vmm/io/ppt.c
+++ b/sys/amd64/vmm/io/ppt.c
@@ -363,6 +363,7 @@ ppt_assign_device(struct vm *vm, int bus, int slot, int func)
 			return (EBUSY);
 
 		ppt->vm = vm;
+		iommu_remove_device(iommu_host_domain(), pci_get_rid(ppt->dev));
 		iommu_add_device(vm_iommu_domain(vm), pci_get_rid(ppt->dev));
 		return (0);
 	}
@@ -385,6 +386,7 @@ ppt_unassign_device(struct vm *vm, int bus, int slot, int func)
 		ppt_teardown_msi(ppt);
 		ppt_teardown_msix(ppt);
 		iommu_remove_device(vm_iommu_domain(vm), pci_get_rid(ppt->dev));
+		iommu_add_device(iommu_host_domain(), pci_get_rid(ppt->dev));
 		ppt->vm = NULL;
 		return (0);
 	}