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Message-ID: <503EC9FE.90000@cn.fujitsu.com>
Date: Thu, 30 Aug 2012 10:03:42 +0800
From: Wen Congyang <wency@...fujitsu.com>
To: Sasha Levin <levinsasha928@...il.com>
CC: kvm list <kvm@...r.kernel.org>, qemu-devel <qemu-devel@...gnu.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Avi Kivity <avi@...hat.com>,
"Daniel P. Berrange" <berrange@...hat.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Jan Kiszka <jan.kiszka@...mens.com>,
Gleb Natapov <gleb@...hat.com>,
Blue Swirl <blauwirbel@...il.com>,
Eric Blake <eblake@...hat.com>,
Andrew Jones <drjones@...hat.com>,
Marcelo Tosatti <mtosatti@...hat.com>,
Anthony Liguori <aliguori@...ibm.com>
Subject: Re: [PATCH v10] kvm: notify host when the guest is panicked
At 08/29/2012 07:56 PM, Sasha Levin Wrote:
> On 08/29/2012 07:18 AM, Wen Congyang 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@...fujitsu.com>
>> ---
>> Documentation/virtual/kvm/pv_event.txt | 32 ++++++++++++++++++++++++++++++++
>> arch/ia64/include/asm/kvm_para.h | 14 ++++++++++++++
>> arch/powerpc/include/asm/kvm_para.h | 14 ++++++++++++++
>> arch/s390/include/asm/kvm_para.h | 14 ++++++++++++++
>> arch/x86/include/asm/kvm_para.h | 27 +++++++++++++++++++++++++++
>> arch/x86/kernel/kvm.c | 25 +++++++++++++++++++++++++
>> include/linux/kvm_para.h | 23 +++++++++++++++++++++++
>> 7 files changed, 149 insertions(+), 0 deletions(-)
>> create mode 100644 Documentation/virtual/kvm/pv_event.txt
>>
>> diff --git a/Documentation/virtual/kvm/pv_event.txt b/Documentation/virtual/kvm/pv_event.txt
>> new file mode 100644
>> index 0000000..bb04de0
>> --- /dev/null
>> +++ b/Documentation/virtual/kvm/pv_event.txt
>> @@ -0,0 +1,32 @@
>> +The KVM paravirtual event interface
>> +=================================
>> +
>> +Initializing the paravirtual event interface
>> +======================
>> +kvm_pv_event_init()
>> +Argiments:
>> + None
>> +
>> +Return Value:
>> + 0: The guest kernel can use paravirtual event interface.
>> + 1: The guest kernel can't use paravirtual event interface.
>> +
>> +Querying whether the event can be ejected
>> +======================
>> +kvm_pv_has_feature()
>> +Arguments:
>> + feature: The bit value of this paravirtual event to query
>> +
>> +Return Value:
>> + 0 : The guest kernel can't eject this paravirtual event.
>> + -1: The guest kernel can eject this paravirtual event.
>> +
>> +
>> +Ejecting paravirtual event
>> +======================
>> +kvm_pv_eject_event()
>> +Arguments:
>> + event: The event to be ejected.
>> +
>> +Return Value:
>> + None
>
> What's the protocol for communicating with the hypervisor? What is it supposed
> to do on reads/writes to that ioport?
Not only ioport, the other arch can use some other ways. We can use
these APIs to eject event to hypervisor. The caller does not care how
to communicate with the hypervisor.
>
>> diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
>> index 2f7712e..7d297f0 100644
>> --- a/arch/x86/include/asm/kvm_para.h
>> +++ b/arch/x86/include/asm/kvm_para.h
>> @@ -96,8 +96,11 @@ 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)
>> +
>> #ifdef __KERNEL__
>> #include <asm/processor.h>
>> +#include <linux/ioport.h>
>>
>> extern void kvmclock_init(void);
>> extern int kvm_register_clock(char *txt);
>> @@ -228,6 +231,30 @@ 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, 1, "KVM_PV_EVENT"))
>
> Only one byte is requested here, but the rest of the code is reading/writing longs?
>
> The struct resource * returned from request_region is simply being leaked here?
>
> What happens if we go ahead with adding another event (let's say OOM event)?
> request_region() is going to fail for anything but the first call.
For x86, we use ioport to communicate with hypervisor. We can read a 32bit value
from the hypervisor. If the bit0 is setted, it means the hypervisor supports
panicked event. If you want add another event, you can use another unused bit.
I think 32 events are enough now.
You can write a value to the ioport to eject the event. Only one event can be
ejected at a time.
>
>> + return -1;
>
> This return value doesn't correspond with the documentation.
Yes, I will update the document. Thanks for pointing it out.
>
>> +
>> + return 0;
>> +}
>> +
>> +static inline unsigned int kvm_arch_pv_features(void)
>> +{
>> + unsigned int features = inl(KVM_PV_EVENT_PORT);
>> +
>> + /* Reading from an invalid I/O port will return -1 */
>
> Just wondering, where is that documented? For lkvm for example the return value
> from an ioport without a device on the other side is undefined, so it's possible
> we're doing something wrong there.
Hmm, how to use lkvm? Can you give me a example. So I can test this patch on lkvm.
For qemu, it returns -1. I don't know which is right now. I will investigate it.
>
>> + if (features == ~0)
>> + features = 0;
>> +
>> + return features;
>> +}
>> +
>> +static inline void kvm_arch_pv_eject_event(unsigned int event)
>> +{
>> + outl(event, KVM_PV_EVENT_PORT);
>> +}
>> +
>> #endif /* __KERNEL__ */
>>
>> #endif /* _ASM_X86_KVM_PARA_H */
>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>> index c1d61ee..6129459 100644
>> --- a/arch/x86/kernel/kvm.c
>> +++ b/arch/x86/kernel/kvm.c
>> @@ -368,6 +368,17 @@ 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;
>> +}
>> +
>> +static struct notifier_block kvm_pv_panic_nb = {
>> + .notifier_call = kvm_pv_panic_notify,
>> +};
>> +
>> static u64 kvm_steal_clock(int cpu)
>> {
>> u64 steal;
>> @@ -447,6 +458,20 @@ 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_event_init())
>> + return;
>> +
>> + if (kvm_pv_has_feature(KVM_PV_FEATURE_PANICKED))
>> + atomic_notifier_chain_register(&panic_notifier_list,
>> + &kvm_pv_panic_nb);
>> +}
>> +arch_initcall(kvm_pv_panicked_event_init);
>
> So it starts automatically on boot? Is there a way to disable it?
Hmm, there is no way to disable it now.
Thanks
Wen Congyang
>
>
> Thanks,
> Sasha
>
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