Re: [PATCH v36 05/31] usb: host: xhci: Notify xHCI sideband on transfer ring free

[Puma Hsu]

On Wed, Mar 19, 2025 at 8:52 AM Wesley Cheng <quic_wcheng@xxxxxxxxxxx> wrote:
>
> 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.
>
> Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>

Tested-by: Puma Hsu <pumahsu@xxxxxxxxxx>

> ---
>  drivers/usb/host/xhci-sideband.c  | 29 ++++++++++++++++++++++++++++-
>  drivers/usb/host/xhci.c           |  3 +++
>  include/linux/usb/xhci-sideband.h | 30 +++++++++++++++++++++++++++++-
>  3 files changed, 60 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideband.c
> index 742bbc6c2d9b..d49f9886dd84 100644
> --- a/drivers/usb/host/xhci-sideband.c
> +++ b/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);
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 61950a350432..91e2d6eac8b7 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/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"
> @@ -3919,6 +3920,8 @@ 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);
>                 }
> diff --git a/include/linux/usb/xhci-sideband.h b/include/linux/usb/xhci-sideband.h
> index f8722afb8a2d..45288c392f6e 100644
> --- a/include/linux/usb/xhci-sideband.h
> +++ b/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 */
>