usb: host: xhci: Notify xHCI sideband on transfer ring free

JIRA: https://issues.redhat.com/browse/RHEL-116016

commit b85a2eb
Author: Wesley Cheng <quic_wcheng@quicinc.com>
Date: Wed, 9 Apr 2025 12:47:38 -0700

  In the case of handling a USB bus reset, the xhci_discover_or_reset_device
  can run without first notifying the xHCI sideband client driver to stop or
  prevent the use of the transfer ring.  It was seen that when a bus reset
  situation happened, the USB offload driver was attempting to fetch the xHCI
  transfer ring information, which was already freed.

  Tested-by: Puma Hsu <pumahsu@google.com>
  Tested-by: Daehwan Jung <dh10.jung@samsung.com>
  Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
  Acked-by: Mark Brown <broonie@kernel.org>
  Link: https://lore.kernel.org/r/20250409194804.3773260-6-quic_wcheng@quicinc.com
  Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Desnes Nunes <desnesn@redhat.com>

Author: Desnes Nunes

drivers/usb/host/xhci-sideband.c

@@ -88,6 +88,30 @@ __xhci_sideband_remove_endpoint(struct xhci_sideband *sb, struct xhci_virt_ep *e
 
 /* sideband api functions */
 
+/**
+ * xhci_sideband_notify_ep_ring_free - notify client of xfer ring free
+ * @sb: sideband instance for this usb device
+ * @ep_index: usb endpoint index
+ *
+ * Notifies the xHCI sideband client driver of a xHCI transfer ring free
+ * routine.  This will allow for the client to ensure that all transfers
+ * are completed.
+ *
+ * The callback should be synchronous, as the ring free happens after.
+ */
+void xhci_sideband_notify_ep_ring_free(struct xhci_sideband *sb,
+				       unsigned int ep_index)
+{
+	struct xhci_sideband_event evt;
+
+	evt.type = XHCI_SIDEBAND_XFER_RING_FREE;
+	evt.evt_data = &ep_index;
+
+	if (sb->notify_client)
+		sb->notify_client(sb->intf, &evt);
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_notify_ep_ring_free);
+
 /**
  * xhci_sideband_add_endpoint - add endpoint to sideband access list
  * @sb: sideband instance for this usb device
@@ -342,7 +366,9 @@ EXPORT_SYMBOL_GPL(xhci_sideband_interrupter_id);
  * Return: pointer to a new xhci_sideband instance if successful. NULL otherwise.
  */
 struct xhci_sideband *
-xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type)
+xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type,
+		       int (*notify_client)(struct usb_interface *intf,
+				    struct xhci_sideband_event *evt))
 {
 	struct usb_device *udev = interface_to_usbdev(intf);
 	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
@@ -381,6 +407,7 @@ xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type)
 	sb->vdev = vdev;
 	sb->intf = intf;
 	sb->type = type;
+	sb->notify_client = notify_client;
 	vdev->sideband = sb;
 
 	spin_unlock_irq(&xhci->lock);

drivers/usb/host/xhci.c

@@ -20,6 +20,7 @@
 #include <linux/string_choices.h>
 #include <linux/dmi.h>
 #include <linux/dma-mapping.h>
+#include <linux/usb/xhci-sideband.h>
 
 #include "xhci.h"
 #include "xhci-trace.h"
@@ -3911,6 +3912,8 @@ static int xhci_discover_or_reset_device(struct usb_hcd *hcd,
 		}
 
 		if (ep->ring) {
+			if (ep->sideband)
+				xhci_sideband_notify_ep_ring_free(ep->sideband, i);
 			xhci_debugfs_remove_endpoint(xhci, virt_dev, i);
 			xhci_free_endpoint_ring(xhci, virt_dev, i);
 		}

include/linux/usb/xhci-sideband.h

@@ -21,6 +21,20 @@ enum xhci_sideband_type {
 	XHCI_SIDEBAND_VENDOR,
 };
 
+enum xhci_sideband_notify_type {
+	XHCI_SIDEBAND_XFER_RING_FREE,
+};
+
+/**
+ * struct xhci_sideband_event - sideband event
+ * @type: notifier type
+ * @evt_data: event data
+ */
+struct xhci_sideband_event {
+	enum xhci_sideband_notify_type type;
+	void *evt_data;
+};
+
 /**
  * struct xhci_sideband - representation of a sideband accessed usb device.
  * @xhci: The xhci host controller the usb device is connected to
@@ -30,6 +44,7 @@ enum xhci_sideband_type {
  * @type: xHCI sideband type
  * @mutex: mutex for sideband operations
  * @intf: USB sideband client interface
+ * @notify_client: callback for xHCI sideband sequences
  *
  * FIXME usb device accessed via sideband Keeping track of sideband accessed usb devices.
  */
@@ -44,10 +59,14 @@ struct xhci_sideband {
 	struct mutex			mutex;
 
 	struct usb_interface		*intf;
+	int (*notify_client)(struct usb_interface *intf,
+			     struct xhci_sideband_event *evt);
 };
 
 struct xhci_sideband *
-xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type);
+xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type,
+		       int (*notify_client)(struct usb_interface *intf,
+				    struct xhci_sideband_event *evt));
 void
 xhci_sideband_unregister(struct xhci_sideband *sb);
 int
@@ -71,4 +90,13 @@ void
 xhci_sideband_remove_interrupter(struct xhci_sideband *sb);
 int
 xhci_sideband_interrupter_id(struct xhci_sideband *sb);
+
+#if IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND)
+void xhci_sideband_notify_ep_ring_free(struct xhci_sideband *sb,
+				       unsigned int ep_index);
+#else
+static inline void xhci_sideband_notify_ep_ring_free(struct xhci_sideband *sb,
+						     unsigned int ep_index)
+{ }
+#endif /* IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND) */
 #endif /* __LINUX_XHCI_SIDEBAND_H */