[QEMU HCI-8.0 PATCH v2 11/13] usb-host: reconfigure endpoints on CPR incoming #VSTOR-137800

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

On CPR incoming we skip the usb_host_open() rescan, so libusb only sets
up the endpoints from the device's default configuration.  If the guest
had enabled an endpoint by selecting a non-zero altsetting (e.g. an
isochronous streaming endpoint), that endpoint is now missing, and the
guest's transfers to it simply stall.

The altsetting itself is restored by vmload now, so let's call
usb_host_ep_update() on the CPR target to rebuild the endpoints out of
it.

The rescan is also the only place where we claim the interfaces in
libusb.  The kernel claims are still there on the preserved FD, but
libusb's own handle knows nothing about them, so a later SET_INTERFACE
would fail with LIBUSB_ERROR_NOT_FOUND.  Let's re-claim the interfaces on
the target as well to bring libusb's view back in sync - on the
preserved FD this is a no-op at the usbfs level anyway.

Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
---
 hw/usb/host-libusb.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/hw/usb/host-libusb.c b/hw/usb/host-libusb.c
index 59f2b151cd2..d12e04c2768 100644
--- a/hw/usb/host-libusb.c
+++ b/hw/usb/host-libusb.c
@@ -1956,6 +1956,34 @@ static void usb_host_post_load_bh(void *opaque)
     usb_host_auto_check(NULL);
 }
 
+/*
+ * On the CPR target libusb knows nothing about the interface claims the
+ * preserved fd still holds, so a later SET_INTERFACE would fail with
+ * NOT_FOUND.  Re-claim them to bring libusb's view back in sync; on the
+ * preserved fd it's a no-op at the usbfs level anyway.
+ */
+static void usb_host_cpr_reclaim_interfaces(USBHostDevice *s)
+{
+    USBDevice *udev = USB_DEVICE(s);
+    struct libusb_config_descriptor *conf;
+    int i, n;
+
+    if (libusb_get_active_config_descriptor(s->dev, &conf) != 0) {
+        return;
+    }
+
+    n = MIN(conf->bNumInterfaces, USB_MAX_INTERFACES);
+    for (i = 0; i < n; i++) {
+        if (libusb_claim_interface(s->dh, i) == 0) {
+            s->ifs[i].claimed = true;
+        }
+    }
+
+    udev->ninterfaces = conf->bNumInterfaces;
+    udev->configuration = conf->bConfigurationValue;
+    libusb_free_config_descriptor(conf);
+}
+
 static int usb_host_post_load(void *opaque, int version_id)
 {
     USBHostDevice *dev = opaque;
@@ -1967,6 +1995,13 @@ static int usb_host_post_load(void *opaque, int version_id)
      * Skip it for CPR.
      */
     if (cpr_is_incoming()) {
+        /*
+         * We kept the device open across CPR, so libusb still needs its
+         * interface claims and endpoints rebuilt here.  And we only start
+         * reaping now, once the source has handed the fd off to us.
+         */
+        usb_host_cpr_reclaim_interfaces(dev);
+        usb_host_ep_update(dev);
         usb_host_cpr_restart_events();
         return 0;
     }
-- 
2.47.1