From: Matt Evans <matt@xxxxxxxxxx>
On weakly-ordered systems, the reading of an event's content must occur
after reading the event's validity.
Signed-off-by: Matt Evans <matt@xxxxxxxxxx>
Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
---
drivers/usb/host/xhci-ring.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9b1eeb0..e0f05f5 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2193,6 +2193,11 @@ static void xhci_handle_event(struct xhci_hcd *xhci)
}
xhci_dbg(xhci, "%s - OS owns TRB\n", __func__);
+ /*
+ * Barrier between reading the TRB_CYCLE (valid) flag above and any
+ * speculative reads of the event's flags/data below.
+ */
+ rmb();
/* FIXME: Handle more event types. */
switch ((le32_to_cpu(event->event_cmd.flags) & TRB_TYPE_BITMASK)) {
case TRB_TYPE(TRB_COMPLETION):
--
1.7.1
--
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