arm-autonomy: Fix xenbus probe for guest kernels < 5.10.17

The arm64-autonomy-guest kernel from commit 3499ba8198ca ("xen: Fix event
channel callback via INTX/GSI") are hanging at `xen🎈 Initialising
balloon driver`.

The arm-autonomy-guest kernels older than 5.10.17 need to backport the
0001-arm-xen-Don-t-probe-xenbus-as-part-of-an-early-initc.patch in order
to be able to boot.

Issue-Id: SCM-2151
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Change-Id: I74f58366f42733be4f67ab3841584efa1636abbb
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm-autonomy/recipes-kernel/linux/files/0001-arm-xen-Don-t-probe-xenbus-as-part-of-an-early-initc.patch

@@ -0,0 +1,95 @@
+From 89b0c20d80a1ab8aa155af287ff4af378862964f Mon Sep 17 00:00:00 2001
+Message-Id: <89b0c20d80a1ab8aa155af287ff4af378862964f.1613583742.git.diego.sueiro@arm.com>
+From: Julien Grall <jgrall@amazon.com>
+Date: Wed, 10 Feb 2021 17:06:54 +0000
+Subject: [PATCH] arm/xen: Don't probe xenbus as part of an early initcall
+
+commit c4295ab0b485b8bc50d2264bcae2acd06f25caaf upstream.
+
+After Commit 3499ba8198cad ("xen: Fix event channel callback via
+INTX/GSI"), xenbus_probe() will be called too early on Arm. This will
+recent to a guest hang during boot.
+
+If the hang wasn't there, we would have ended up to call
+xenbus_probe() twice (the second time is in xenbus_probe_initcall()).
+
+We don't need to initialize xenbus_probe() early for Arm guest.
+Therefore, the call in xen_guest_init() is now removed.
+
+After this change, there is no more external caller for xenbus_probe().
+So the function is turned to a static one. Interestingly there were two
+prototypes for it.
+
+Cc: stable@vger.kernel.org
+Fixes: 3499ba8198cad ("xen: Fix event channel callback via INTX/GSI")
+Reported-by: Ian Jackson <iwj@xenproject.org>
+Signed-off-by: Julien Grall <jgrall@amazon.com>
+Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
+Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
+Link: https://lore.kernel.org/r/20210210170654.5377-1-julien@xen.org
+Signed-off-by: Juergen Gross <jgross@suse.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+Upstream-Status: Backport
+Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
+---
+ arch/arm/xen/enlighten.c          | 2 --
+ drivers/xen/xenbus/xenbus.h       | 1 -
+ drivers/xen/xenbus/xenbus_probe.c | 2 +-
+ include/xen/xenbus.h              | 2 --
+ 4 files changed, 1 insertion(+), 6 deletions(-)
+
+diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
+index 5a957a9a0984..8ad576ecd0f1 100644
+--- a/arch/arm/xen/enlighten.c
++++ b/arch/arm/xen/enlighten.c
+@@ -370,8 +370,6 @@ static int __init xen_guest_init(void)
+ 		return -ENOMEM;
+ 	}
+ 	gnttab_init();
+-	if (!xen_initial_domain())
+-		xenbus_probe();
+ 
+ 	/*
+ 	 * Making sure board specific code will not set up ops for
+diff --git a/drivers/xen/xenbus/xenbus.h b/drivers/xen/xenbus/xenbus.h
+index dc1537335414..2a93b7c9c159 100644
+--- a/drivers/xen/xenbus/xenbus.h
++++ b/drivers/xen/xenbus/xenbus.h
+@@ -115,7 +115,6 @@ int xenbus_probe_node(struct xen_bus_type *bus,
+ 		      const char *type,
+ 		      const char *nodename);
+ int xenbus_probe_devices(struct xen_bus_type *bus);
+-void xenbus_probe(void);
+ 
+ void xenbus_dev_changed(const char *node, struct xen_bus_type *bus);
+ 
+diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
+index 18ffd0551b54..8a75092bb148 100644
+--- a/drivers/xen/xenbus/xenbus_probe.c
++++ b/drivers/xen/xenbus/xenbus_probe.c
+@@ -683,7 +683,7 @@ void unregister_xenstore_notifier(struct notifier_block *nb)
+ }
+ EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);
+ 
+-void xenbus_probe(void)
++static void xenbus_probe(void)
+ {
+ 	xenstored_ready = 1;
+ 
+diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
+index 2c43b0ef1e4d..bf3cfc7c35d0 100644
+--- a/include/xen/xenbus.h
++++ b/include/xen/xenbus.h
+@@ -192,8 +192,6 @@ void xs_suspend_cancel(void);
+ 
+ struct work_struct;
+ 
+-void xenbus_probe(void);
+-
+ #define XENBUS_IS_ERR_READ(str) ({			\
+ 	if (!IS_ERR(str) && strlen(str) == 0) {		\
+ 		kfree(str);				\
+-- 
+2.17.1
+

meta-arm-autonomy/recipes-kernel/linux/linux-arm-autonomy.inc

@@ -49,4 +49,9 @@ python() {
        and not pn.startswith('linux-linaro-arm') \
        and oe.utils.any_distro_features(d, "arm-autonomy-host"):
         d.appendVar('SRC_URI', ' file://files/0001-xen-Fix-XenStore-initialisation-for-XS_LOCAL.patch' )
+
+    if kernelVersion and LooseVersion(kernelVersion) < '5.10.17' \
+       and pn != 'linux-libc-headers' \
+       and oe.utils.any_distro_features(d, "arm-autonomy-guest"):
+        d.appendVar('SRC_URI', ' file://files/0001-arm-xen-Don-t-probe-xenbus-as-part-of-an-early-initc.patch' )
 }