Re: [PATCH v12 rebased] kvm: notify host when the guest is panicked

From: Hu Tao
Date: Thu Feb 28 2013 - 03:54:25 EST

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On Thu, Feb 07, 2013 at 11:39:47PM -0200, Marcelo Tosatti wrote:
> Hi,
>
> On Wed, Jan 23, 2013 at 03:19:21PM +0800, Hu Tao wrote:
> > 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 starting the kernel
> >
> > Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
> > Signed-off-by: Hu Tao <hutao@xxxxxxxxxxxxxx>
> > ---
> > arch/ia64/kvm/irq.h | 19 +++++++++++++
> > arch/powerpc/include/asm/kvm_para.h | 18 ++++++++++++
> > arch/s390/include/asm/kvm_para.h | 19 +++++++++++++
> > arch/x86/include/asm/kvm_para.h | 20 ++++++++++++++
> > arch/x86/include/uapi/asm/kvm_para.h | 2 ++
> > arch/x86/kernel/kvm.c | 53 ++++++++++++++++++++++++++++++++++++
> > include/linux/kvm_para.h | 18 ++++++++++++
> > include/uapi/linux/kvm_para.h | 6 ++++
> > kernel/panic.c | 4 +++
> > 9 files changed, 159 insertions(+)
> >
> > diff --git a/arch/ia64/kvm/irq.h b/arch/ia64/kvm/irq.h
> > index c0785a7..b3870f8 100644
> > --- a/arch/ia64/kvm/irq.h
> > +++ b/arch/ia64/kvm/irq.h
> > @@ -30,4 +30,23 @@ static inline int irqchip_in_kernel(struct kvm *kvm)
> > return 1;
> > }
> >
> > +static inline int kvm_arch_pv_event_init(void)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline unsigned int kvm_arch_pv_features(void)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline void kvm_arch_pv_eject_event(unsigned int event)
> > +{
> > +}
> > +
> > +static inline bool kvm_arch_pv_event_enabled(void)
> > +{
> > + return false;
> > +}
> > +
>
> The interface is x86 only, no need to touch other architectures.

OK.

>
> > #endif
> > diff --git a/arch/powerpc/include/asm/kvm_para.h b/arch/powerpc/include/asm/kvm_para.h
> > index 2b11965..17dd013 100644
> > --- a/arch/powerpc/include/asm/kvm_para.h
> > +++ b/arch/powerpc/include/asm/kvm_para.h
> > @@ -144,4 +144,22 @@ static inline bool kvm_check_and_clear_guest_paused(void)
> > return false;
> > }
> >
> > +static inline int kvm_arch_pv_event_init(void)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline unsigned int kvm_arch_pv_features(void)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline void kvm_arch_pv_eject_event(unsigned int event)
> > +{
> > +}
> > +
> > +static inline bool kvm_arch_pv_event_enabled(void)
> > +{
> > + return false;
> > +}
> > #endif /* __POWERPC_KVM_PARA_H__ */
> > diff --git a/arch/s390/include/asm/kvm_para.h b/arch/s390/include/asm/kvm_para.h
> > index e0f8423..81d87ec 100644
> > --- a/arch/s390/include/asm/kvm_para.h
> > +++ b/arch/s390/include/asm/kvm_para.h
> > @@ -154,4 +154,23 @@ static inline bool kvm_check_and_clear_guest_paused(void)
> > return false;
> > }
> >
> > +static inline int kvm_arch_pv_event_init(void)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline unsigned int kvm_arch_pv_features(void)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline void kvm_arch_pv_eject_event(unsigned int event)
> > +{
> > +}
> > +
> > +static inline bool kvm_arch_pv_event_enabled(void)
> > +{
> > + return false;
> > +}
> > +
> > #endif /* __S390_KVM_PARA_H */
> > --- a/arch/x86/include/asm/kvm_para.h
> > +++ b/arch/x86/include/asm/kvm_para.h
> > @@ -133,4 +133,24 @@ static inline void kvm_disable_steal_time(void)
> > }
> > #endif
> >
> > +static inline int kvm_arch_pv_event_init(void)
> > +{
> > + if (!request_region(KVM_PV_EVENT_PORT, 4, "KVM_PV_EVENT"))
> > + return -1;
> > +
> > + return 0;
> > +}
>
> This should be in a driver in arch/x86/kernel/kvm-panic.c, or so.
>
> > +
> > +static inline unsigned int kvm_arch_pv_features(void)
> > +{
> > + return inl(KVM_PV_EVENT_PORT);
> > +}
> > +
> > +static inline void kvm_arch_pv_eject_event(unsigned int event)
> > +{
> > + outl(event, KVM_PV_EVENT_PORT);
> > +}
>
> > +
> > +bool kvm_arch_pv_event_enabled(void);
> > +
> > #endif /* _ASM_X86_KVM_PARA_H */
> > diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
> > index 06fdbd9..c15ef33 100644
> > --- a/arch/x86/include/uapi/asm/kvm_para.h
> > +++ b/arch/x86/include/uapi/asm/kvm_para.h
> > @@ -96,5 +96,7 @@ struct kvm_vcpu_pv_apf_data {
> > #define KVM_PV_EOI_ENABLED KVM_PV_EOI_MASK
> > #define KVM_PV_EOI_DISABLED 0x0
> >
> > +#define KVM_PV_EVENT_PORT (0x505UL)
> > +
>
> No need for the ioport to be hard coded. What are the options to
> communicate an address to the guest? An MSR, via ACPI?

I'm not quite understanding here. By 'address', you mean an ioport?
how to communicate an address? (I have little knowledge about ACPI)

>
> >
> > #endif /* _UAPI_ASM_X86_KVM_PARA_H */
> > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> > index 9c2bd8b..0aa7b3e 100644
> > --- a/arch/x86/kernel/kvm.c
> > +++ b/arch/x86/kernel/kvm.c
> > @@ -73,6 +73,20 @@ static int parse_no_kvmclock_vsyscall(char *arg)
> >
> > early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
> >
> > +static int pv_event = 1;
> > +static int parse_no_pv_event(char *arg)
> > +{
> > + pv_event = 0;
> > + return 0;
> > +}
> > +
> > +bool kvm_arch_pv_event_enabled(void)
> > +{
> > + return !!pv_event;
> > +}
> > +
> > +early_param("no-pv-event", parse_no_pv_event);
> > +
>
> "pv-event" is a bad name for an interface which is specific to notify
> panic events. Please use pv-panic everywhere.

panic event is one of the events supported. Can we keep the name?

>
> > static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
> > static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
> > static int has_steal_clock = 0;
> > @@ -385,6 +399,17 @@ 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)
> > +{
> > + kvm_pv_eject_event(KVM_PV_EVENT_PANICKED);
> > + return NOTIFY_DONE;
> > +}
>
> Why 'eject' ?

changed to 'send'

>
> > +
> > +static struct notifier_block kvm_pv_panic_nb = {
> > + .notifier_call = kvm_pv_panic_notify,
> > +};
> > +
> > static u64 kvm_steal_clock(int cpu)
> > {
> > u64 steal;
> > @@ -462,6 +487,34 @@ static void __init kvm_apf_trap_init(void)
> > set_intr_gate(14, &async_page_fault);
> > }
> >
> > +static void __init kvm_pv_panicked_event_init(void)
> > +{
> > + if (!kvm_para_available())
> > + return;
> > +
> > + if (kvm_pv_has_feature(KVM_PV_FEATURE_PANICKED))
> > + atomic_notifier_chain_register(&panic_notifier_list,
> > + &kvm_pv_panic_nb);
> > +}
> > +
> > +static inline int kvm_pv_event_init(void)
> > +{
> > + return kvm_arch_pv_event_init();
> > +}
> > +
> > +static int __init enable_pv_event(void)
> > +{
> > + if (pv_event) {
> > + if (kvm_pv_event_init())
> > + return 0;
> > +
> > + kvm_pv_panicked_event_init();
> > + }
> > +
> > + return 0;
> > +}
> > +arch_initcall(enable_pv_event);
>
> Call the initialization code from kvm_guest_init, only one function is
> necessary.

At the point of kvm_guest_init, rqeust_region (called by
kvm_pv_event_init) will block, so the guest kernel won't up.

>
> > +
> > void __init kvm_guest_init(void)
> > {
> > int i;
> > diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
> > index 00a97bb..6fb6198 100644
> > --- a/include/linux/kvm_para.h
> > +++ b/include/linux/kvm_para.h
> > @@ -10,4 +10,22 @@ 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;
> > +}
> > +
> > +static inline void kvm_pv_eject_event(unsigned int event)
> > +{
> > + kvm_arch_pv_eject_event(event);
> > +}
> > +
> > +static inline bool kvm_pv_event_enabled(void)
> > +{
> > + return kvm_arch_pv_event_enabled();
> > +}
>
> No need for this helpers, as noted.

OK.

>
> > #endif /* __LINUX_KVM_PARA_H */
> > diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
> > index cea2c5c..c41ddce 100644
> > --- a/include/uapi/linux/kvm_para.h
> > +++ b/include/uapi/linux/kvm_para.h
> > @@ -20,6 +20,12 @@
> > #define KVM_HC_FEATURES 3
> > #define KVM_HC_PPC_MAP_MAGIC_PAGE 4
> >
> > +/* The bit of supported pv event */
> > +#define KVM_PV_FEATURE_PANICKED 0
> > +
> > +/* The pv event value */
> > +#define KVM_PV_EVENT_PANICKED 1
> > +
>
> This is a hypercall header. You want
>
> arch/x86/include/asm/kvm_para.h

OK.

>
> > /*
> > * hypercalls use architecture specific
> > */
> > diff --git a/kernel/panic.c b/kernel/panic.c
> > index e1b2822..a764d2e 100644
> > --- a/kernel/panic.c
> > +++ b/kernel/panic.c
> > @@ -23,6 +23,7 @@
> > #include <linux/init.h>
> > #include <linux/nmi.h>
> > #include <linux/dmi.h>
> > +#include <linux/kvm_para.h>
> >
> > #define PANIC_TIMER_STEP 100
> > #define PANIC_BLINK_SPD 18
> > @@ -132,6 +133,9 @@ void panic(const char *fmt, ...)
> > if (!panic_blink)
> > panic_blink = no_blink;
> >
> > + if (kvm_pv_event_enabled())
> > + panic_timeout = 0;
> > +
>
> What is the rationale behind this?

This is a hack to disable reset_on_panic if user enables
pv-event.
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