On boot, enabling errata workarounds will be triggered by the boot CPU
from start_xen(). On CPU hotplug (non-boot scenario) this would not be
done. This patch adds the code required to enable errata workarounds for
a CPU being hotplugged after the system boots. This is triggered using
a notifier. If the CPU fails to enable workarounds the notifier will
return an error and Xen will hit the BUG_ON() in notify_cpu_starting().
To avoid the BUG_ON() in an error case either enabling notifiers should
be fixed to return void (not propagate error to notify_cpu_starting())
and the errata notifier will always return success for CPU_STARTING
event, or the notify_cpu_starting() and other common code should be
fixed to expect an error at CPU_STARTING phase.
Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
---
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
---
Changes in v4:
-Add includes alphabetically
-Added newline before the return in cpu_errata_notifier_init()
-Enabling capabilities returns an error if enabling a capability fails
(enable_nonboot_cpu_caps() returns int instead of void). When enabling
any of the capability fails the error is remembered into a variable and
the remaining capabilities are enabled. If enabling multiple capabilities
fails the error returned by enable_nonboot_cpu_caps() represents the
error code of the last failure.
-Callback enable_nonboot_cpu_caps() can return an error when CPU_STARTING
fires. This is not right because of the assumption that starting a CPU
cannot fail at this phase. Consequently, if an error happens it will
cause Xen to hit the BUG_ON() in notify_cpu_starting(). In future,
either this notifier/enabling capabilities should be fixed to always
return success/void, or notify_cpu_starting() and other common code
should be fixed to expect an error at CPU_STARTING phase.
-Fix commit message to reflect changes in v4
---
xen/arch/arm/cpuerrata.c | 49 ++++++++++++++++++++++++++++++++++++++++
xen/arch/arm/cpufeature.c | 29 ++++++++++++++++++++++++
xen/include/asm-arm/cpufeature.h | 1 +
3 files changed, 79 insertions(+)
diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c
index 1baa20654b..b829d226ef 100644
--- a/xen/arch/arm/cpuerrata.c
+++ b/xen/arch/arm/cpuerrata.c
@@ -1,3 +1,4 @@
+#include <xen/cpu.h>
#include <xen/cpumask.h>
#include <xen/mm.h>
#include <xen/sizes.h>
@@ -5,6 +6,7 @@
#include <xen/spinlock.h>
#include <xen/vmap.h>
#include <xen/warning.h>
+#include <xen/notifier.h>
#include <asm/cpufeature.h>
#include <asm/cpuerrata.h>
#include <asm/psci.h>
@@ -349,6 +351,53 @@ void __init enable_errata_workarounds(void)
enable_cpu_capabilities(arm_errata);
}
+static int cpu_errata_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
+{
+ int rc = 0;
+
+ switch ( action )
+ {
+ case CPU_STARTING:
+ /*
+ * At CPU_STARTING phase no notifier shall return an error, because the
+ * system is designed with the assumption that starting a CPU cannot
+ * fail at this point. If an error happens here it will cause Xen to
hit
+ * the BUG_ON() in notify_cpu_starting(). In future, either this
+ * notifier/enabling capabilities should be fixed to always return
+ * success/void or notify_cpu_starting() and other common code should
be
+ * fixed to expect an error at CPU_STARTING phase.
+ */
+ ASSERT(system_state != SYS_STATE_boot);
+ rc = enable_nonboot_cpu_caps(arm_errata);
+ break;
+ default:
+ break;
+ }
+
+ return !rc ? NOTIFY_DONE : notifier_from_errno(rc);
+}
+
+static struct notifier_block cpu_errata_nfb = {
+ .notifier_call = cpu_errata_callback,
+};
+
+static int __init cpu_errata_notifier_init(void)
+{
+ register_cpu_notifier(&cpu_errata_nfb);
+
+ return 0;
+}
+/*
+ * Initialization has to be done at init rather than presmp_init phase because
+ * the callback should execute only after the secondary CPUs are initially
+ * booted (in hotplug scenarios when the system state is not boot). On boot,
+ * the enabling of errata workarounds will be triggered by the boot CPU from
+ * start_xen().
+ */
+__initcall(cpu_errata_notifier_init);
+
/*
* Local variables:
* mode: C
diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
index 525b45e22f..3aaff4c0e6 100644
--- a/xen/arch/arm/cpufeature.c
+++ b/xen/arch/arm/cpufeature.c
@@ -69,6 +69,35 @@ void __init enable_cpu_capabilities(const struct
arm_cpu_capabilities *caps)
}
/*
+ * Run through the enabled capabilities and enable() them on the calling CPU.
+ * If enabling of any capability fails the error is returned. After enabling a
+ * capability fails the error will be remembered into 'rc' and the remaining
+ * capabilities will be enabled. If enabling multiple capabilities fail the
+ * error returned by this function represents the error code of the last
+ * failure.
+ */
+int enable_nonboot_cpu_caps(const struct arm_cpu_capabilities *caps)
+{
+ int rc = 0;
+
+ for ( ; caps->matches; caps++ )
+ {
+ if ( !cpus_have_cap(caps->capability) )
+ continue;
+
+ if ( caps->enable )
+ {
+ int ret = caps->enable((void *)caps);
+
+ if ( ret )
+ rc = ret;
+ }
+ }
+
+ return rc;
+}
+
+/*
* Local variables:
* mode: C
* c-file-style: "BSD"
diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
index e557a095af..c5d046218b 100644
--- a/xen/include/asm-arm/cpufeature.h
+++ b/xen/include/asm-arm/cpufeature.h
@@ -88,6 +88,7 @@ void update_cpu_capabilities(const struct
arm_cpu_capabilities *caps,
const char *info);
void enable_cpu_capabilities(const struct arm_cpu_capabilities *caps);
+int enable_nonboot_cpu_caps(const struct arm_cpu_capabilities *caps);
#endif /* __ASSEMBLY__ */
