Merge branch 'master' into openslx

11 files changed, 175 insertions, 39 deletions

diff --git a/src/drivers/bus/pci.c b/src/drivers/bus/pci.c
index 1b7350c8b..5891e42ff 100644
--- a/src/drivers/bus/pci.c
+++ b/src/drivers/bus/pci.c
@@ -121,6 +121,11 @@ static void pci_read_bases ( struct pci_device *pci ) {
 	unsigned long bar;
 	int reg;
 
+	/* Clear any existing base addresses */
+	pci->ioaddr = 0;
+	pci->membase = 0;
+
+	/* Get first memory and I/O BAR addresses */
 	for ( reg = PCI_BASE_ADDRESS_0; reg <= PCI_BASE_ADDRESS_5; reg += 4 ) {
 		bar = pci_bar ( pci, reg );
 		if ( bar & PCI_BASE_ADDRESS_SPACE_IO ) {
diff --git a/src/drivers/bus/virtio-pci.c b/src/drivers/bus/virtio-pci.c
index 5d2d62750..8b34c7277 100644
--- a/src/drivers/bus/virtio-pci.c
+++ b/src/drivers/bus/virtio-pci.c
@@ -17,37 +17,47 @@
 #include "ipxe/io.h"
 #include "ipxe/iomap.h"
 #include "ipxe/pci.h"
+#include "ipxe/dma.h"
 #include "ipxe/reboot.h"
 #include "ipxe/virtio-pci.h"
 #include "ipxe/virtio-ring.h"
 
-static int vp_alloc_vq(struct vring_virtqueue *vq, u16 num)
+static int vp_alloc_vq(struct vring_virtqueue *vq, u16 num, size_t header_size)
 {
-    size_t queue_size = PAGE_MASK + vring_size(num);
+    size_t ring_size = PAGE_MASK + vring_size(num);
     size_t vdata_size = num * sizeof(void *);
+    size_t queue_size = ring_size + vdata_size + header_size;
 
-    vq->queue = zalloc(queue_size + vdata_size);
+    vq->queue = dma_alloc(vq->dma, &vq->map, queue_size, queue_size);
     if (!vq->queue) {
         return -ENOMEM;
     }
 
+    memset ( vq->queue, 0, queue_size );
+    vq->queue_size = queue_size;
+
     /* vdata immediately follows the ring */
-    vq->vdata = (void **)(vq->queue + queue_size);
+    vq->vdata = (void **)(vq->queue + ring_size);
+
+    /* empty header immediately follows vdata */
+    vq->empty_header = (struct virtio_net_hdr_modern *)(vq->queue + ring_size + vdata_size);
 
     return 0;
 }
 
 void vp_free_vq(struct vring_virtqueue *vq)
 {
-    if (vq->queue) {
-        free(vq->queue);
+    if (vq->queue && vq->queue_size) {
+        dma_free(&vq->map, vq->queue, vq->queue_size);
         vq->queue = NULL;
         vq->vdata = NULL;
+        vq->queue_size = 0;
     }
 }
 
 int vp_find_vq(unsigned int ioaddr, int queue_index,
-               struct vring_virtqueue *vq)
+               struct vring_virtqueue *vq, struct dma_device *dma_dev,
+               size_t header_size)
 {
    struct vring * vr = &vq->vring;
    u16 num;
@@ -73,9 +83,10 @@ int vp_find_vq(unsigned int ioaddr, int queue_index,
    }
 
    vq->queue_index = queue_index;
+   vq->dma = dma_dev;
 
    /* initialize the queue */
-   rc = vp_alloc_vq(vq, num);
+   rc = vp_alloc_vq(vq, num, header_size);
    if (rc) {
            DBG("VIRTIO-PCI ERROR: failed to allocate queue memory\n");
            return rc;
@@ -87,8 +98,7 @@ int vp_find_vq(unsigned int ioaddr, int queue_index,
     * NOTE: vr->desc is initialized by vring_init()
     */
 
-   outl((unsigned long)virt_to_phys(vr->desc) >> PAGE_SHIFT,
-        ioaddr + VIRTIO_PCI_QUEUE_PFN);
+   outl(dma(&vq->map, vr->desc) >> PAGE_SHIFT, ioaddr + VIRTIO_PCI_QUEUE_PFN);
 
    return num;
 }
@@ -348,7 +358,8 @@ void vpm_notify(struct virtio_pci_modern_device *vdev,
 }
 
 int vpm_find_vqs(struct virtio_pci_modern_device *vdev,
-                 unsigned nvqs, struct vring_virtqueue *vqs)
+                 unsigned nvqs, struct vring_virtqueue *vqs,
+                 struct dma_device *dma_dev, size_t header_size)
 {
     unsigned i;
     struct vring_virtqueue *vq;
@@ -392,11 +403,12 @@ int vpm_find_vqs(struct virtio_pci_modern_device *vdev,
 
         vq = &vqs[i];
         vq->queue_index = i;
+        vq->dma = dma_dev;
 
         /* get offset of notification word for this vq */
         off = vpm_ioread16(vdev, &vdev->common, COMMON_OFFSET(queue_notify_off));
 
-        err = vp_alloc_vq(vq, size);
+        err = vp_alloc_vq(vq, size, header_size);
         if (err) {
             DBG("VIRTIO-PCI %p: failed to allocate queue memory\n", vdev);
             return err;
@@ -406,13 +418,16 @@ int vpm_find_vqs(struct virtio_pci_modern_device *vdev,
         /* activate the queue */
         vpm_iowrite16(vdev, &vdev->common, size, COMMON_OFFSET(queue_size));
 
-        vpm_iowrite64(vdev, &vdev->common, virt_to_phys(vq->vring.desc),
+        vpm_iowrite64(vdev, &vdev->common,
+                      dma(&vq->map, vq->vring.desc),
                       COMMON_OFFSET(queue_desc_lo),
                       COMMON_OFFSET(queue_desc_hi));
-        vpm_iowrite64(vdev, &vdev->common, virt_to_phys(vq->vring.avail),
+        vpm_iowrite64(vdev, &vdev->common,
+                      dma(&vq->map, vq->vring.avail),
                       COMMON_OFFSET(queue_avail_lo),
                       COMMON_OFFSET(queue_avail_hi));
-        vpm_iowrite64(vdev, &vdev->common, virt_to_phys(vq->vring.used),
+        vpm_iowrite64(vdev, &vdev->common,
+                      dma(&vq->map, vq->vring.used),
                       COMMON_OFFSET(queue_used_lo),
                       COMMON_OFFSET(queue_used_hi));
 
diff --git a/src/drivers/bus/virtio-ring.c b/src/drivers/bus/virtio-ring.c
index 98e787e16..e448c3488 100644
--- a/src/drivers/bus/virtio-ring.c
+++ b/src/drivers/bus/virtio-ring.c
@@ -98,7 +98,7 @@ void vring_add_buf(struct vring_virtqueue *vq,
    for (i = head; out; i = vr->desc[i].next, out--) {
 
            vr->desc[i].flags = VRING_DESC_F_NEXT;
-           vr->desc[i].addr = (u64)virt_to_phys(list->addr);
+           vr->desc[i].addr = list->addr;
            vr->desc[i].len = list->length;
            prev = i;
            list++;
@@ -106,7 +106,7 @@ void vring_add_buf(struct vring_virtqueue *vq,
    for ( ; in; i = vr->desc[i].next, in--) {
 
            vr->desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
-           vr->desc[i].addr = (u64)virt_to_phys(list->addr);
+           vr->desc[i].addr = list->addr;
            vr->desc[i].len = list->length;
            prev = i;
            list++;
diff --git a/src/drivers/net/efi/nii.c b/src/drivers/net/efi/nii.c
index b9f34650e..833462e77 100644
--- a/src/drivers/net/efi/nii.c
+++ b/src/drivers/net/efi/nii.c
@@ -576,7 +576,7 @@ static int nii_issue_cpb_db ( struct nii_nic *nii, unsigned int op, void *cpb,
 	cdb.IFnum = nii->nii->IfNum;
 
 	/* Raise task priority level */
-	tpl = bs->RaiseTPL ( TPL_CALLBACK );
+	tpl = bs->RaiseTPL ( efi_internal_tpl );
 
 	/* Issue command */
 	DBGC2 ( nii, "NII %s issuing %02x:%04x ifnum %d%s%s\n",
diff --git a/src/drivers/net/efi/snpnet.c b/src/drivers/net/efi/snpnet.c
index fb5240277..69ec6f5e5 100644
--- a/src/drivers/net/efi/snpnet.c
+++ b/src/drivers/net/efi/snpnet.c
@@ -164,6 +164,10 @@ static int snpnet_transmit ( struct net_device *netdev,
 	EFI_STATUS efirc;
 	int rc;
 
+	/* Do nothing if shutdown is in progress */
+	if ( efi_shutdown_in_progress )
+		return -ECANCELED;
+
 	/* Defer the packet if there is already a transmission in progress */
 	if ( snp->txbuf ) {
 		netdev_tx_defer ( netdev, iobuf );
@@ -283,6 +287,10 @@ static void snpnet_poll_rx ( struct net_device *netdev ) {
  */
 static void snpnet_poll ( struct net_device *netdev ) {
 
+	/* Do nothing if shutdown is in progress */
+	if ( efi_shutdown_in_progress )
+		return;
+
 	/* Process any TX completions */
 	snpnet_poll_tx ( netdev );
 
@@ -426,8 +434,9 @@ static void snpnet_close ( struct net_device *netdev ) {
 	EFI_STATUS efirc;
 	int rc;
 
-	/* Shut down NIC */
-	if ( ( efirc = snp->snp->Shutdown ( snp->snp ) ) != 0 ) {
+	/* Shut down NIC (unless whole system shutdown is in progress) */
+	if ( ( ! efi_shutdown_in_progress ) &&
+	     ( ( efirc = snp->snp->Shutdown ( snp->snp ) ) != 0 ) ) {
 		rc = -EEFI ( efirc );
 		DBGC ( snp, "SNP %s could not shut down: %s\n",
 		       netdev->name, strerror ( rc ) );
@@ -589,8 +598,9 @@ void snpnet_stop ( struct efi_device *efidev ) {
 	/* Unregister network device */
 	unregister_netdev ( netdev );
 
-	/* Stop SNP protocol */
-	if ( ( efirc = snp->snp->Stop ( snp->snp ) ) != 0 ) {
+	/* Stop SNP protocol (unless whole system shutdown is in progress) */
+	if ( ( ! efi_shutdown_in_progress ) &&
+	     ( ( efirc = snp->snp->Stop ( snp->snp ) ) != 0 ) ) {
 		rc = -EEFI ( efirc );
 		DBGC ( device, "SNP %s could not stop: %s\n",
 		       efi_handle_name ( device ), strerror ( rc ) );
diff --git a/src/drivers/net/intelx.c b/src/drivers/net/intelx.c
index ccf6b0648..f4dad8859 100644
--- a/src/drivers/net/intelx.c
+++ b/src/drivers/net/intelx.c
@@ -481,6 +481,7 @@ static struct pci_device_id intelx_nics[] = {
 	PCI_ROM ( 0x8086, 0x15ab, "x552", "X552", 0 ),
 	PCI_ROM ( 0x8086, 0x15c8, "x553t", "X553/X557-AT", 0 ),
 	PCI_ROM ( 0x8086, 0x15ce, "x553-sfp", "X553 (SFP+)", 0 ),
+	PCI_ROM ( 0x8086, 0x15e4, "x553a", "X553", 0 ),
 	PCI_ROM ( 0x8086, 0x15e5, "x553", "X553", 0 ),
 };
 
diff --git a/src/drivers/net/virtio-net.c b/src/drivers/net/virtio-net.c
index 78ec9ac4e..0c4541924 100644
--- a/src/drivers/net/virtio-net.c
+++ b/src/drivers/net/virtio-net.c
@@ -29,6 +29,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <ipxe/iobuf.h>
 #include <ipxe/netdevice.h>
 #include <ipxe/pci.h>
+#include <ipxe/dma.h>
 #include <ipxe/if_ether.h>
 #include <ipxe/ethernet.h>
 #include <ipxe/virtio-pci.h>
@@ -99,8 +100,9 @@ struct virtnet_nic {
 	/** Pending rx packet count */
 	unsigned int rx_num_iobufs;
 
-	/** Virtio net dummy packet headers */
-	struct virtio_net_hdr_modern empty_header[QUEUE_NB];
+	/** DMA device */
+	struct dma_device *dma;
+
 };
 
 /** Add an iobuf to a virtqueue
@@ -115,7 +117,7 @@ static void virtnet_enqueue_iob ( struct net_device *netdev,
 				  int vq_idx, struct io_buffer *iobuf ) {
 	struct virtnet_nic *virtnet = netdev->priv;
 	struct vring_virtqueue *vq = &virtnet->virtqueue[vq_idx];
-	struct virtio_net_hdr_modern *header = &virtnet->empty_header[vq_idx];
+	struct virtio_net_hdr_modern *header = vq->empty_header;
 	unsigned int out = ( vq_idx == TX_INDEX ) ? 2 : 0;
 	unsigned int in = ( vq_idx == TX_INDEX ) ? 0 : 2;
 	size_t header_len = ( virtnet->virtio_version ?
@@ -132,11 +134,11 @@ static void virtnet_enqueue_iob ( struct net_device *netdev,
 			 * to header->flags for received packets.  Work around
 			 * this by using separate RX and TX headers.
 			 */
-			.addr = ( char* ) header,
+			.addr = dma ( &vq->map, header ),
 			.length = header_len,
 		},
 		{
-			.addr = ( char* ) iobuf->data,
+			.addr = iob_dma ( iobuf ),
 			.length = iob_len ( iobuf ),
 		},
 	};
@@ -161,7 +163,7 @@ static void virtnet_refill_rx_virtqueue ( struct net_device *netdev ) {
 		struct io_buffer *iobuf;
 
 		/* Try to allocate a buffer, stop for now if out of memory */
-		iobuf = alloc_iob ( len );
+		iobuf = alloc_rx_iob ( len, virtnet->dma );
 		if ( ! iobuf )
 			break;
 
@@ -215,7 +217,8 @@ static int virtnet_open_legacy ( struct net_device *netdev ) {
 
 	/* Initialize rx/tx virtqueues */
 	for ( i = 0; i < QUEUE_NB; i++ ) {
-		if ( vp_find_vq ( ioaddr, i, &virtnet->virtqueue[i] ) == -1 ) {
+		if ( vp_find_vq ( ioaddr, i, &virtnet->virtqueue[i], virtnet->dma,
+                                  sizeof ( struct virtio_net_hdr_modern ) ) == -1 ) {
 			DBGC ( virtnet, "VIRTIO-NET %p cannot register queue %d\n",
 			       virtnet, i );
 			virtnet_free_virtqueues ( netdev );
@@ -280,7 +283,8 @@ static int virtnet_open_modern ( struct net_device *netdev ) {
 	}
 
 	/* Initialize rx/tx virtqueues */
-	if ( vpm_find_vqs ( &virtnet->vdev, QUEUE_NB, virtnet->virtqueue ) ) {
+	if ( vpm_find_vqs ( &virtnet->vdev, QUEUE_NB, virtnet->virtqueue,
+                            virtnet->dma, sizeof ( struct virtio_net_hdr_modern ) ) ) {
 		DBGC ( virtnet, "VIRTIO-NET %p cannot register queues\n",
 		       virtnet );
 		virtnet_free_virtqueues ( netdev );
@@ -335,7 +339,7 @@ static void virtnet_close ( struct net_device *netdev ) {
 
 	/* Free rx iobufs */
 	list_for_each_entry_safe ( iobuf, next_iobuf, &virtnet->rx_iobufs, list ) {
-		free_iob ( iobuf );
+		free_rx_iob ( iobuf );
 	}
 	INIT_LIST_HEAD ( &virtnet->rx_iobufs );
 	virtnet->rx_num_iobufs = 0;
@@ -478,6 +482,12 @@ static int virtnet_probe_legacy ( struct pci_device *pci ) {
 
 	/* Enable PCI bus master and reset NIC */
 	adjust_pci_device ( pci );
+
+	/* Configure DMA */
+	virtnet->dma =  &pci->dma;
+	dma_set_mask_64bit ( virtnet->dma );
+	netdev->dma = virtnet->dma;
+
 	vp_reset ( ioaddr );
 
 	/* Load MAC address and MTU */
@@ -506,7 +516,7 @@ static int virtnet_probe_legacy ( struct pci_device *pci ) {
 	return 0;
 
 	unregister_netdev ( netdev );
- err_register_netdev:
+err_register_netdev:
 	vp_reset ( ioaddr );
 	netdev_nullify ( netdev );
 	netdev_put ( netdev );
@@ -586,6 +596,11 @@ static int virtnet_probe_modern ( struct pci_device *pci, int *found_dev ) {
 	/* Enable the PCI device */
 	adjust_pci_device ( pci );
 
+	/* Configure DMA */
+	virtnet->dma =  &pci->dma;
+	dma_set_mask_64bit ( virtnet->dma );
+	netdev->dma = virtnet->dma;
+
 	/* Reset the device and set initial status bits */
 	vpm_reset ( &virtnet->vdev );
 	vpm_add_status ( &virtnet->vdev, VIRTIO_CONFIG_S_ACKNOWLEDGE );
@@ -633,7 +648,6 @@ err_mac_address:
 	vpm_reset ( &virtnet->vdev );
 	netdev_nullify ( netdev );
 	netdev_put ( netdev );
-
 	virtio_pci_unmap_capability ( &virtnet->vdev.device );
 err_map_device:
 	virtio_pci_unmap_capability ( &virtnet->vdev.isr );
diff --git a/src/drivers/usb/usbkbd.c b/src/drivers/usb/usbkbd.c
index a8ab6ab76..b284e584f 100644
--- a/src/drivers/usb/usbkbd.c
+++ b/src/drivers/usb/usbkbd.c
@@ -25,10 +25,12 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 #include <stdlib.h>
 #include <string.h>
+#include <ctype.h>
 #include <errno.h>
 #include <assert.h>
 #include <ipxe/console.h>
 #include <ipxe/keys.h>
+#include <ipxe/keymap.h>
 #include <ipxe/usb.h>
 #include "usbkbd.h"
 
@@ -69,10 +71,7 @@ static unsigned int usbkbd_map ( unsigned int keycode, unsigned int modifiers,
 	} else if ( keycode <= USBKBD_KEY_Z ) {
 		/* Alphabetic keys */
 		key = ( keycode - USBKBD_KEY_A + 'a' );
-		if ( modifiers & USBKBD_CTRL ) {
-			key -= ( 'a' - CTRL_A );
-		} else if ( ( modifiers & USBKBD_SHIFT ) ||
-			    ( leds & USBKBD_LED_CAPS_LOCK ) ) {
+		if ( modifiers & USBKBD_SHIFT ) {
 			key -= ( 'a' - 'A' );
 		}
 	} else if ( keycode <= USBKBD_KEY_0 ) {
@@ -118,10 +117,30 @@ static unsigned int usbkbd_map ( unsigned int keycode, unsigned int modifiers,
 			};
 			key = keypad[ keycode - USBKBD_KEY_PAD_1 ];
 		};
+	} else if ( keycode == USBKBD_KEY_NON_US ) {
+		/* Non-US \ and | */
+		key = ( ( modifiers & USBKBD_SHIFT ) ?
+			( KEYMAP_PSEUDO | '|' ) : ( KEYMAP_PSEUDO | '\\' ) );
 	} else {
 		key = 0;
 	}
 
+	/* Remap key if applicable */
+	if ( ( keycode < USBKBD_KEY_CAPS_LOCK ) ||
+	     ( keycode == USBKBD_KEY_NON_US ) ) {
+
+		/* Apply modifiers */
+		if ( modifiers & USBKBD_CTRL )
+			key |= KEYMAP_CTRL;
+		if ( modifiers & USBKBD_ALT_RIGHT )
+			key |= KEYMAP_ALTGR;
+		if ( leds & USBKBD_LED_CAPS_LOCK )
+			key |= KEYMAP_CAPSLOCK;
+
+		/* Remap key */
+		key = key_remap ( key );
+	}
+
 	return key;
 }
 
diff --git a/src/drivers/usb/usbkbd.h b/src/drivers/usb/usbkbd.h
index cedebfe71..1a3fea1ba 100644
--- a/src/drivers/usb/usbkbd.h
+++ b/src/drivers/usb/usbkbd.h
@@ -75,6 +75,7 @@ enum usb_keycode {
 	USBKBD_KEY_PAD_ENTER = 0x58,
 	USBKBD_KEY_PAD_1 = 0x59,
 	USBKBD_KEY_PAD_DOT = 0x63,
+	USBKBD_KEY_NON_US = 0x64,
 };
 
 /** USB keyboard LEDs */
diff --git a/src/drivers/usb/xhci.c b/src/drivers/usb/xhci.c
index cc48af033..3247ee69c 100644
--- a/src/drivers/usb/xhci.c
+++ b/src/drivers/usb/xhci.c
@@ -1165,6 +1165,31 @@ static int xhci_reset ( struct xhci_device *xhci ) {
 	return -ETIMEDOUT;
 }
 
+/**
+ * Mark xHCI device as permanently failed
+ *
+ * @v xhci		xHCI device
+ * @ret rc		Return status code
+ */
+static int xhci_fail ( struct xhci_device *xhci ) {
+	size_t len;
+	int rc;
+
+	/* Mark command mechanism as permanently failed */
+	xhci->failed = 1;
+
+	/* Reset device */
+	if ( ( rc = xhci_reset ( xhci ) ) != 0 )
+		return rc;
+
+	/* Discard DCBAA entries since DCBAAP has been cleared */
+	assert ( xhci->dcbaa.context != NULL );
+	len = ( ( xhci->slots + 1 ) * sizeof ( xhci->dcbaa.context[0] ) );
+	memset ( xhci->dcbaa.context, 0, len );
+
+	return 0;
+}
+
 /******************************************************************************
  *
  * Transfer request blocks
@@ -1720,6 +1745,10 @@ static void xhci_event_poll ( struct xhci_device *xhci ) {
 	unsigned int consumed;
 	unsigned int type;
 
+	/* Do nothing if device has permanently failed */
+	if ( xhci->failed )
+		return;
+
 	/* Poll for events */
 	profile_start ( &xhci_event_profiler );
 	for ( consumed = 0 ; ; consumed++ ) {
@@ -1778,6 +1807,7 @@ static void xhci_event_poll ( struct xhci_device *xhci ) {
  */
 static void xhci_abort ( struct xhci_device *xhci ) {
 	physaddr_t crp;
+	uint32_t crcr;
 
 	/* Abort the command */
 	DBGC2 ( xhci, "XHCI %s aborting command\n", xhci->name );
@@ -1786,8 +1816,18 @@ static void xhci_abort ( struct xhci_device *xhci ) {
 	/* Allow time for command to abort */
 	mdelay ( XHCI_COMMAND_ABORT_DELAY_MS );
 
-	/* Sanity check */
-	assert ( ( readl ( xhci->op + XHCI_OP_CRCR ) & XHCI_CRCR_CRR ) == 0 );
+	/* Check for failure to abort */
+	crcr = readl ( xhci->op + XHCI_OP_CRCR );
+	if ( crcr & XHCI_CRCR_CRR ) {
+
+		/* Device has failed to abort a command and is almost
+		 * certainly beyond repair.  Reset device, abandoning
+		 * all state, and mark device as failed to avoid
+		 * delays on any future command attempts.
+		 */
+		DBGC ( xhci, "XHCI %s failed to abort command\n", xhci->name );
+		xhci_fail ( xhci );
+	}
 
 	/* Consume (and ignore) any final command status */
 	xhci_event_poll ( xhci );
@@ -1813,6 +1853,12 @@ static int xhci_command ( struct xhci_device *xhci, union xhci_trb *trb ) {
 	unsigned int i;
 	int rc;
 
+	/* Immediately fail all commands if command mechanism has failed */
+	if ( xhci->failed ) {
+		rc = -EPIPE;
+		goto err_failed;
+	}
+
 	/* Sanity check */
 	if ( xhci->pending ) {
 		DBGC ( xhci, "XHCI %s command ring busy\n", xhci->name );
@@ -1863,6 +1909,7 @@ static int xhci_command ( struct xhci_device *xhci, union xhci_trb *trb ) {
  err_enqueue:
 	xhci->pending = NULL;
  err_pending:
+ err_failed:
 	return rc;
 }
 
@@ -3412,14 +3459,36 @@ static int xhci_probe ( struct pci_device *pci ) {
 static void xhci_remove ( struct pci_device *pci ) {
 	struct xhci_device *xhci = pci_get_drvdata ( pci );
 	struct usb_bus *bus = xhci->bus;
+	uint16_t command;
+
+	/* Some systems are observed to disable bus mastering on
+	 * Thunderbolt controllers before we get a chance to shut
+	 * down.  Detect this and avoid attempting any DMA operations,
+	 * which are guaranteed to fail and may end up spuriously
+	 * completing after the operating system kernel starts up.
+	 */
+	pci_read_config_word ( pci, PCI_COMMAND, &command );
+	if ( ! ( command & PCI_COMMAND_MASTER ) ) {
+		DBGC ( xhci, "XHCI %s DMA was disabled\n", xhci->name );
+		xhci_fail ( xhci );
+	}
 
+	/* Unregister and free USB bus */
 	unregister_usb_bus ( bus );
 	free_usb_bus ( bus );
+
+	/* Reset device and undo any PCH-specific fixes */
 	xhci_reset ( xhci );
 	if ( xhci->quirks & XHCI_PCH )
 		xhci_pch_undo ( xhci, pci );
+
+	/* Release ownership back to BIOS */
 	xhci_legacy_release ( xhci );
+
+	/* Unmap registers */
 	iounmap ( xhci->regs );
+
+	/* Free device */
 	free ( xhci );
 }
 
diff --git a/src/drivers/usb/xhci.h b/src/drivers/usb/xhci.h
index 6e02d70e0..a3c8888af 100644
--- a/src/drivers/usb/xhci.h
+++ b/src/drivers/usb/xhci.h
@@ -1115,6 +1115,8 @@ struct xhci_device {
 	struct xhci_event_ring event;
 	/** Current command (if any) */
 	union xhci_trb *pending;
+	/** Command mechanism has permanently failed */
+	int failed;
 
 	/** Device slots, indexed by slot ID */
 	struct xhci_slot **slot;