diff mbox series

[3/3] usb: xhci: Notify xen when DbC is unsafe to use

Message ID 2af7e7b8d569e94ab9c48039040ca69a8d52c89d.1620776161.git.connojdavis@gmail.com (mailing list archive)
State New
Headers show
Series Support xen-driven USB3 debug capability | expand

Commit Message

Connor Davis May 12, 2021, 12:18 a.m. UTC
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 <connojdavis@gmail.com>
---
 drivers/usb/host/xhci-dbgcap.h |  6 ++++
 drivers/usb/host/xhci.c        | 57 ++++++++++++++++++++++++++++++++++
 drivers/usb/host/xhci.h        |  1 +
 3 files changed, 64 insertions(+)

--
2.31.1

Comments

Greg KH May 12, 2021, 7:03 a.m. UTC | #1
On Tue, May 11, 2021 at 06:18:21PM -0600, Connor Davis wrote:
> 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 <connojdavis@gmail.com>
> ---
>  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?

thanks,

greg k-h
Connor Davis May 12, 2021, 2:59 p.m. UTC | #2
On May 12, 21, Greg Kroah-Hartman wrote:
> On Tue, May 11, 2021 at 06:18:21PM -0600, Connor Davis wrote:
> > 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 <connojdavis@gmail.com>
> > ---
> >  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
diff mbox series

Patch

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>
+
+static void xhci_dbc_external_reset_prep(struct xhci_hcd *xhci)
+{
+	struct dbc_regs __iomem *regs;
+	void __iomem		*base;
+	int			dbc_cap;
+
+	if (!xen_initial_domain())
+		return;
+
+	base = &xhci->cap_regs->hc_capbase;
+	dbc_cap = xhci_find_next_ext_cap(base, 0, XHCI_EXT_CAPS_DEBUG);
+
+	if (!dbc_cap)
+		return;
+
+	xhci->external_dbc = 0;
+	regs = base + dbc_cap;
+
+	if (readl(&regs->control) & DBC_CTRL_DBC_ENABLE) {
+		if (xen_dbgp_reset_prep(xhci_to_hcd(xhci)))
+			xhci_dbg_trace(xhci, trace_xhci_dbg_init,
+					"// Failed to reset external DBC");
+		else {
+			xhci->external_dbc = 1;
+			xhci_dbg_trace(xhci, trace_xhci_dbg_init,
+					"// Completed reset of external DBC");
+		}
+	}
+}
+
+static void xhci_dbc_external_reset_done(struct xhci_hcd *xhci)
+{
+	if (!xen_initial_domain() || !xhci->external_dbc)
+		return;
+
+	if (xen_dbgp_external_startup(xhci_to_hcd(xhci)))
+		xhci->external_dbc = 0;
+}
+#else
+static void xhci_dbc_external_reset_prep(struct xhci_hcd *xhci)
+{
+}
+
+static void xhci_dbc_external_reset_done(struct xhci_hcd *xhci)
+{
+}
+#endif
+
 static bool td_on_ring(struct xhci_td *td, struct xhci_ring *ring)
 {
 	struct xhci_segment *seg = ring->first_seg;
@@ -180,6 +231,8 @@  int xhci_reset(struct xhci_hcd *xhci)
 		return 0;
 	}

+	xhci_dbc_external_reset_prep(xhci);
+
 	xhci_dbg_trace(xhci, trace_xhci_dbg_init, "// Reset the HC");
 	command = readl(&xhci->op_regs->command);
 	command |= CMD_RESET;
@@ -211,6 +264,8 @@  int xhci_reset(struct xhci_hcd *xhci)
 	 */
 	ret = xhci_handshake(&xhci->op_regs->status,
 			STS_CNR, 0, 10 * 1000 * 1000);
+	if (!ret)
+		xhci_dbc_external_reset_done(xhci);

 	xhci->usb2_rhub.bus_state.port_c_suspend = 0;
 	xhci->usb2_rhub.bus_state.suspended_ports = 0;
@@ -991,6 +1046,7 @@  int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup)
 		return 0;

 	xhci_dbc_suspend(xhci);
+	xhci_dbc_external_reset_prep(xhci);

 	/* Don't poll the roothubs on bus suspend. */
 	xhci_dbg(xhci, "%s: stopping port polling.\n", __func__);
@@ -1225,6 +1281,7 @@  int xhci_resume(struct xhci_hcd *xhci, bool hibernated)
 	spin_unlock_irq(&xhci->lock);

 	xhci_dbc_resume(xhci);
+	xhci_dbc_external_reset_done(xhci);

  done:
 	if (retval == 0) {
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 2595a8f057c4..61d8efc9eef2 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1920,6 +1920,7 @@  struct xhci_hcd {
 	struct list_head	regset_list;

 	void			*dbc;
+	int			external_dbc;
 	/* platform-specific data -- must come last */
 	unsigned long		priv[] __aligned(sizeof(s64));
 };