[v3 2/5] arm64: kvm: allow EL2 context to be reset on shutdown

AKASHI Takahiro
2015-04-02T05:41:12Z

The current kvm implementation keeps EL2 vector table installed even
when the system is shut down. This prevents kexec from putting the system
with kvm back into EL2 when starting a new kernel.

This patch resolves this issue by calling a cpu tear-down function via
reboot notifier, kvm_reboot_notify(), which is invoked by
kernel_restart_prepare() in kernel_kexec().
While kvm has a generic hook, kvm_reboot(), we can't use it here because
a cpu teardown function will not be invoked, under current implementation,
if no guest vm has been created by kvm_create_vm().
Please note that kvm_usage_count is zero in this case.

We'd better, in the future, implement cpu hotplug support and put the
arch-specific initialization into kvm_arch_hardware_enable/disable().
This way, we would be able to revert this patch.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
---
arch/arm/kvm/arm.c | 21 +++++++++++++++++++++
arch/arm64/kvm/Kconfig | 1 -
2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 39df694..f64713e 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -25,6 +25,7 @@
#include <linux/vmalloc.h>
#include <linux/fs.h>
#include <linux/mman.h>
+#include <linux/reboot.h>
#include <linux/sched.h>
#include <linux/kvm.h>
#include <trace/events/kvm.h>
@@ -1100,6 +1101,23 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr)
return NULL;
}

+static int kvm_reboot_notify(struct notifier_block *nb,
+ unsigned long val, void *v)
+{
+ /*
+ * Reset each CPU in EL2 to initial state.
+ */
+ on_each_cpu(kvm_cpu_reset, NULL, 1);
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block kvm_reboot_nb = {
+ .notifier_call = kvm_reboot_notify,
+ .next = NULL,
+ .priority = 0, /* FIXME */
+};
+
/**
* Initialize Hyp-mode and memory mappings on all CPUs.
*/
@@ -1138,6 +1156,9 @@ int kvm_arch_init(void *opaque)
hyp_cpu_pm_init();

kvm_coproc_table_init();
+
+ register_reboot_notifier(&kvm_reboot_nb);
+
return 0;
out_err:
cpu_notifier_register_done();
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 30ae7a7..f5590c8 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -18,7 +18,6 @@ if VIRTUALIZATION

config KVM
bool "Kernel-based Virtual Machine (KVM) support"
- depends on !KEXEC
select MMU_NOTIFIER
select PREEMPT_NOTIFIERS
select ANON_INODES
--
1.7.9.5