Merge tag 'for-linus-5.16c-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen fixes from Juergen Gross:

 - Kconfig fix to make it possible to control building of the privcmd
   driver

 - three fixes for issues identified by the kernel test robot

 - a five-patch series to simplify timeout handling for Xen PV driver
   initialization

 - two patches to fix error paths in xenstore/xenbus driver
   initialization

* tag 'for-linus-5.16c-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: make HYPERVISOR_set_debugreg() always_inline
  xen: make HYPERVISOR_get_debugreg() always_inline
  xen: detect uninitialized xenbus in xenbus_init
  xen: flag xen_snd_front to be not essential for system boot
  xen: flag pvcalls-front to be not essential for system boot
  xen: flag hvc_xen to be not essential for system boot
  xen: flag xen_drm_front to be not essential for system boot
  xen: add "not_essential" flag to struct xenbus_driver
  xen/pvh: add missing prototype to header
  xen: don't continue xenstore initialization in case of errors
  xen/privcmd: make option visible in Kconfig

8 files changed, 41 insertions, 13 deletions

diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c
index 9f14d99c763c..bc7605324db3 100644
--- a/drivers/gpu/drm/xen/xen_drm_front.c
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -773,6 +773,7 @@ static struct xenbus_driver xen_driver = {
 	.probe = xen_drv_probe,
 	.remove = xen_drv_remove,
 	.otherend_changed = displback_changed,
+	.not_essential = true,
 };
 
 static int __init xen_drv_init(void)
diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
index 4ff5cd2a6d8d..3d17a0b3fe51 100644
--- a/drivers/input/misc/xen-kbdfront.c
+++ b/drivers/input/misc/xen-kbdfront.c
@@ -542,6 +542,7 @@ static struct xenbus_driver xenkbd_driver = {
 	.remove = xenkbd_remove,
 	.resume = xenkbd_resume,
 	.otherend_changed = xenkbd_backend_changed,
+	.not_essential = true,
 };
 
 static int __init xenkbd_init(void)
diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index f0bf01ea069a..71e0dd2c0ce5 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -522,6 +522,7 @@ static struct xenbus_driver xencons_driver = {
 	.remove = xencons_remove,
 	.resume = xencons_resume,
 	.otherend_changed = xencons_backend_changed,
+	.not_essential = true,
 };
 #endif /* CONFIG_HVC_XEN_FRONTEND */
 
diff --git a/drivers/video/fbdev/xen-fbfront.c b/drivers/video/fbdev/xen-fbfront.c
index 5ec51445bee8..6826f986da43 100644
--- a/drivers/video/fbdev/xen-fbfront.c
+++ b/drivers/video/fbdev/xen-fbfront.c
@@ -695,6 +695,7 @@ static struct xenbus_driver xenfb_driver = {
 	.remove = xenfb_remove,
 	.resume = xenfb_resume,
 	.otherend_changed = xenfb_backend_changed,
+	.not_essential = true,
 };
 
 static int __init xenfb_init(void)
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index a1b11c62da9e..33e941e40082 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -259,9 +259,15 @@ config XEN_SCSI_BACKEND
 	  if guests need generic access to SCSI devices.
 
 config XEN_PRIVCMD
-	tristate
+	tristate "Xen hypercall passthrough driver"
 	depends on XEN
 	default m
+	help
+	  The hypercall passthrough driver allows privileged user programs to
+	  perform Xen hypercalls. This driver is normally required for systems
+	  running as Dom0 to perform privileged operations, but in some
+	  disaggregated Xen setups this driver might be needed for other
+	  domains, too.
 
 config XEN_ACPI_PROCESSOR
 	tristate "Xen ACPI processor"
diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 7984645b5956..3c9ae156b597 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -1275,6 +1275,7 @@ static struct xenbus_driver pvcalls_front_driver = {
 	.probe = pvcalls_front_probe,
 	.remove = pvcalls_front_remove,
 	.otherend_changed = pvcalls_front_changed,
+	.not_essential = true,
 };
 
 static int __init pvcalls_frontend_init(void)
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index bd003ca8acbe..fe360c33ce71 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -909,7 +909,7 @@ static struct notifier_block xenbus_resume_nb = {
 
 static int __init xenbus_init(void)
 {
-	int err = 0;
+	int err;
 	uint64_t v = 0;
 	xen_store_domain_type = XS_UNKNOWN;
 
@@ -949,6 +949,29 @@ static int __init xenbus_init(void)
 		err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
 		if (err)
 			goto out_error;
+		/*
+		 * Uninitialized hvm_params are zero and return no error.
+		 * Although it is theoretically possible to have
+		 * HVM_PARAM_STORE_PFN set to zero on purpose, in reality it is
+		 * not zero when valid. If zero, it means that Xenstore hasn't
+		 * been properly initialized. Instead of attempting to map a
+		 * wrong guest physical address return error.
+		 *
+		 * Also recognize all bits set as an invalid value.
+		 */
+		if (!v || !~v) {
+			err = -ENOENT;
+			goto out_error;
+		}
+		/* Avoid truncation on 32-bit. */
+#if BITS_PER_LONG == 32
+		if (v > ULONG_MAX) {
+			pr_err("%s: cannot handle HVM_PARAM_STORE_PFN=%llx > ULONG_MAX\n",
+			       __func__, v);
+			err = -EINVAL;
+			goto out_error;
+		}
+#endif
 		xen_store_gfn = (unsigned long)v;
 		xen_store_interface =
 			xen_remap(xen_store_gfn << XEN_PAGE_SHIFT,
@@ -983,8 +1006,10 @@ static int __init xenbus_init(void)
 	 */
 	proc_create_mount_point("xen");
 #endif
+	return 0;
 
 out_error:
+	xen_store_domain_type = XS_UNKNOWN;
 	return err;
 }
 
diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c b/drivers/xen/xenbus/xenbus_probe_frontend.c
index 480944606a3c..07b010a68fcf 100644
--- a/drivers/xen/xenbus/xenbus_probe_frontend.c
+++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -211,19 +211,11 @@ static int is_device_connecting(struct device *dev, void *data, bool ignore_none
 	if (drv && (dev->driver != drv))
 		return 0;
 
-	if (ignore_nonessential) {
-		/* With older QEMU, for PVonHVM guests the guest config files
-		 * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
-		 * which is nonsensical as there is no PV FB (there can be
-		 * a PVKB) running as HVM guest. */
+	xendrv = to_xenbus_driver(dev->driver);
 
-		if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
-			return 0;
+	if (ignore_nonessential && xendrv->not_essential)
+		return 0;
 
-		if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
-			return 0;
-	}
-	xendrv = to_xenbus_driver(dev->driver);
 	return (xendev->state < XenbusStateConnected ||
 		(xendev->state == XenbusStateConnected &&
 		 xendrv->is_ready && !xendrv->is_ready(xendev)));