On May 12, 21, Greg Kroah-Hartman wrote:

On Tue, May 11, 2021 at 06:18:21PM -0600, Connor Davis wrote:

quoted

When running as a dom0 guest on Xen, check if the USB3 debug
capability is enabled before xHCI reset, suspend, and resume. If it
is, call xen_dbgp_reset_prep() to notify Xen that it is unsafe to touch
MMIO registers until the next xen_dbgp_external_startup().

This notification allows Xen to avoid undefined behavior resulting
from MMIO access when the host controller's CNR bit is set or when
the device transitions to D3hot.

Signed-off-by: Connor Davis <redacted>
---
 drivers/usb/host/xhci-dbgcap.h |  6 ++++
 drivers/usb/host/xhci.c        | 57 ++++++++++++++++++++++++++++++++++
 drivers/usb/host/xhci.h        |  1 +
 3 files changed, 64 insertions(+)

diff --git a/drivers/usb/host/xhci-dbgcap.h b/drivers/usb/host/xhci-dbgcap.h
index c70b78d504eb..24784b82a840 100644
--- a/drivers/usb/host/xhci-dbgcap.h
+++ b/drivers/usb/host/xhci-dbgcap.h

@@ -227,4 +227,10 @@ static inline int xhci_dbc_resume(struct xhci_hcd *xhci)
 	return 0;
 }
 #endif /* CONFIG_USB_XHCI_DBGCAP */
+
+#ifdef CONFIG_XEN_DOM0
+int xen_dbgp_reset_prep(struct usb_hcd *hcd);
+int xen_dbgp_external_startup(struct usb_hcd *hcd);
+#endif /* CONFIG_XEN_DOM0 */
+
 #endif /* __LINUX_XHCI_DBGCAP_H */

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index ca9385d22f68..afe44169183f 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c

@@ -37,6 +37,57 @@ static unsigned long long quirks;
 module_param(quirks, ullong, S_IRUGO);
 MODULE_PARM_DESC(quirks, "Bit flags for quirks to be enabled as default");

+#ifdef CONFIG_XEN_DOM0
+#include <xen/xen.h>

<snip>

Can't this #ifdef stuff go into a .h file?

Yep, will clean that up in v2.

thanks,

greg k-h

Thanks,
Connor