Commit 0353810a authored by Mathias Nyman's avatar Mathias Nyman Committed by Greg Kroah-Hartman
Browse files

xhci: avoid DMA double fetch when reading event trb type. 



Instead of re-reading, masking and endianness correcting the same trb
several times to get the trb type from an event, just do it once and
store it in a local variable.

Also pass the trb_type directly to the vendor specific event handler,
avoiding one more similar read.

In addition to the security benefit this also cleans up the code
and helps readability.

Signed-off-by: default avatarMathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20210129130044.206855-13-mathias.nyman@linux.intel.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 55f6153d

drivers/usb/host/xhci-ring.c

+12 −15
Original line number Diff line number Diff line
@@ -1564,11 +1564,8 @@ static void handle_cmd_completion(struct xhci_hcd *xhci, 
}



static void handle_vendor_event(struct xhci_hcd *xhci,

		union xhci_trb *event)

				union xhci_trb *event, u32 trb_type)

{

	u32 trb_type;



	trb_type = TRB_FIELD_TO_TYPE(le32_to_cpu(event->generic.field[3]));

	xhci_dbg(xhci, "Vendor specific event TRB type = %u\n", trb_type);

	if (trb_type == TRB_NEC_CMD_COMP && (xhci->quirks & XHCI_NEC_HOST))

		handle_cmd_completion(xhci, &event->event_cmd);
@@ -2733,6 +2730,7 @@ static int xhci_handle_event(struct xhci_hcd *xhci) 
{

	union xhci_trb *event;

	int update_ptrs = 1;

	u32 trb_type;

	int ret;



	/* Event ring hasn't been allocated yet. */
@@ -2754,31 +2752,30 @@ static int xhci_handle_event(struct xhci_hcd *xhci) 
	 * speculative reads of the event's flags/data below.

	 */

	rmb();

	trb_type = TRB_FIELD_TO_TYPE(le32_to_cpu(event->event_cmd.flags));

	/* FIXME: Handle more event types. */

	switch (le32_to_cpu(event->event_cmd.flags) & TRB_TYPE_BITMASK) {

	case TRB_TYPE(TRB_COMPLETION):



	switch (trb_type) {

	case TRB_COMPLETION:

		handle_cmd_completion(xhci, &event->event_cmd);

		break;

	case TRB_TYPE(TRB_PORT_STATUS):

	case TRB_PORT_STATUS:

		handle_port_status(xhci, event);

		update_ptrs = 0;

		break;

	case TRB_TYPE(TRB_TRANSFER):

	case TRB_TRANSFER:

		ret = handle_tx_event(xhci, &event->trans_event);

		if (ret >= 0)

			update_ptrs = 0;

		break;

	case TRB_TYPE(TRB_DEV_NOTE):

	case TRB_DEV_NOTE:

		handle_device_notification(xhci, event);

		break;

	default:

		if ((le32_to_cpu(event->event_cmd.flags) & TRB_TYPE_BITMASK) >=

		    TRB_TYPE(48))

			handle_vendor_event(xhci, event);

		if (trb_type >= TRB_VENDOR_DEFINED_LOW)

			handle_vendor_event(xhci, event, trb_type);

		else

			xhci_warn(xhci, "ERROR unknown event type %d\n",

				  TRB_FIELD_TO_TYPE(

				  le32_to_cpu(event->event_cmd.flags)));

			xhci_warn(xhci, "ERROR unknown event type %d\n", trb_type);

	}

	/* Any of the above functions may drop and re-acquire the lock, so check

	 * to make sure a watchdog timer didn't mark the host as non-responsive.

drivers/usb/host/xhci.h

+1 −1
Original line number Diff line number Diff line
@@ -1419,7 +1419,7 @@ union xhci_trb { 
/* MFINDEX Wrap Event - microframe counter wrapped */

#define TRB_MFINDEX_WRAP	39

/* TRB IDs 40-47 reserved, 48-63 is vendor-defined */



#define TRB_VENDOR_DEFINED_LOW	48

/* Nec vendor-specific command completion event. */

#define	TRB_NEC_CMD_COMP	48

/* Get NEC firmware revision. */