[Qemu-devel] [PATCH v5] kvm: notify host when the guest is panicked

[Wen Congyang]

We can know the guest is panicked when the guest runs on xen.
But we do not have such feature on kvm.

Another purpose of this feature is: management app(for example:
libvirt) can do auto dump when the guest is panicked. If management
app does not do auto dump, the guest's user can do dump by hand if
he sees the guest is panicked.

We have three solutions to implement this feature:
1. use vmcall
2. use I/O port
3. use virtio-serial.

We have decided to avoid touching hypervisor. The reason why I choose
choose the I/O port is:
1. it is easier to implememt
2. it does not depend any virtual device
3. it can work when startint the kernel

Signed-off-by: Wen Congyang <address@hidden>
---
 arch/ia64/include/asm/kvm_para.h    |    5 +++++
 arch/powerpc/include/asm/kvm_para.h |    5 +++++
 arch/s390/include/asm/kvm_para.h    |    5 +++++
 arch/x86/include/asm/kvm_para.h     |    7 +++++++
 arch/x86/kernel/kvm.c               |   14 ++++++++++++++
 include/linux/kvm_para.h            |   13 +++++++++++++
 6 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/arch/ia64/include/asm/kvm_para.h b/arch/ia64/include/asm/kvm_para.h
index 2019cb9..187c0e2 100644
--- a/arch/ia64/include/asm/kvm_para.h
+++ b/arch/ia64/include/asm/kvm_para.h
@@ -31,6 +31,11 @@ static inline bool kvm_check_and_clear_guest_paused(void)
        return false;
 }
 
+static inline unsigned int kvm_arch_pv_features(void)
+{
+       return 0;
+}
+
 #endif
 
 #endif
diff --git a/arch/powerpc/include/asm/kvm_para.h 
b/arch/powerpc/include/asm/kvm_para.h
index c18916b..be81aac 100644
--- a/arch/powerpc/include/asm/kvm_para.h
+++ b/arch/powerpc/include/asm/kvm_para.h
@@ -211,6 +211,11 @@ static inline bool kvm_check_and_clear_guest_paused(void)
        return false;
 }
 
+static inline unsigned int kvm_arch_pv_features(void)
+{
+       return 0;
+}
+
 #endif /* __KERNEL__ */
 
 #endif /* __POWERPC_KVM_PARA_H__ */
diff --git a/arch/s390/include/asm/kvm_para.h b/arch/s390/include/asm/kvm_para.h
index a988329..3d993b7 100644
--- a/arch/s390/include/asm/kvm_para.h
+++ b/arch/s390/include/asm/kvm_para.h
@@ -154,6 +154,11 @@ static inline bool kvm_check_and_clear_guest_paused(void)
        return false;
 }
 
+static inline unsigned int kvm_arch_pv_features(void)
+{
+       return 0;
+}
+
 #endif
 
 #endif /* __S390_KVM_PARA_H */
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 63ab166..c8ad86e 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -89,6 +89,8 @@ struct kvm_vcpu_pv_apf_data {
        __u32 enabled;
 };
 
+#define KVM_PV_PORT    (0x505UL)
+
 #ifdef __KERNEL__
 #include <asm/processor.h>
 
@@ -221,6 +223,11 @@ static inline void kvm_disable_steal_time(void)
 }
 #endif
 
+static inline unsigned int kvm_arch_pv_features(void)
+{
+       return inl(KVM_PV_PORT);
+}
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_X86_KVM_PARA_H */
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index e554e5a..9a97f7e 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -328,6 +328,17 @@ static struct notifier_block kvm_pv_reboot_nb = {
        .notifier_call = kvm_pv_reboot_notify,
 };
 
+static int
+kvm_pv_panic_notify(struct notifier_block *nb, unsigned long code, void 
*unused)
+{
+       outl(KVM_PV_PANICKED, KVM_PV_PORT);
+       return NOTIFY_DONE;
+}
+
+static struct notifier_block kvm_pv_panic_nb = {
+       .notifier_call = kvm_pv_panic_notify,
+};
+
 static u64 kvm_steal_clock(int cpu)
 {
        u64 steal;
@@ -414,6 +425,9 @@ void __init kvm_guest_init(void)
 
        paravirt_ops_setup();
        register_reboot_notifier(&kvm_pv_reboot_nb);
+       if (kvm_pv_has_feature(KVM_PV_FEATURE_PANICKED))
+               atomic_notifier_chain_register(&panic_notifier_list,
+                       &kvm_pv_panic_nb);
        for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
                spin_lock_init(&async_pf_sleepers[i].lock);
        if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
index ff476dd..e73efcf 100644
--- a/include/linux/kvm_para.h
+++ b/include/linux/kvm_para.h
@@ -20,6 +20,12 @@
 #define KVM_HC_FEATURES                        3
 #define KVM_HC_PPC_MAP_MAGIC_PAGE      4
 
+/* The bit of the value read from KVM_PV_PORT */
+#define KVM_PV_FEATURE_PANICKED        0
+
+/* The value writen to KVM_PV_PORT */
+#define KVM_PV_PANICKED                1
+
 /*
  * hypercalls use architecture specific
  */
@@ -33,5 +39,12 @@ static inline int kvm_para_has_feature(unsigned int feature)
                return 1;
        return 0;
 }
+
+static inline int kvm_pv_has_feature(unsigned int feature)
+{
+       if (kvm_arch_pv_features() & (1UL << feature))
+               return 1;
+       return 0;
+}
 #endif /* __KERNEL__ */
 #endif /* __LINUX_KVM_PARA_H */
-- 
1.7.1