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Message-ID: <4F4DF8B0.9000608@cn.fujitsu.com>
Date: Wed, 29 Feb 2012 18:06:40 +0800
From: Wen Congyang <wency@...fujitsu.com>
To: Gleb Natapov <gleb@...hat.com>
CC: Jan Kiszka <jan.kiszka@...mens.com>,
kvm list <kvm@...r.kernel.org>, Avi Kivity <avi@...hat.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
"Daniel P. Berrange" <berrange@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
qemu-devel <qemu-devel@...gnu.org>
Subject: Re: [PATCH] kvm: notify host when guest paniced
At 02/29/2012 05:36 PM, Gleb Natapov Wrote:
> On Wed, Feb 29, 2012 at 09:08:52AM +0800, Wen Congyang wrote:
>> At 02/28/2012 06:45 PM, Gleb Natapov Wrote:
>>> On Tue, Feb 28, 2012 at 11:19:47AM +0100, Jan Kiszka wrote:
>>>> On 2012-02-28 10:42, Wen Congyang wrote:
>>>>> At 02/28/2012 05:34 PM, Jan Kiszka Wrote:
>>>>>> On 2012-02-28 09:23, Wen Congyang wrote:
>>>>>>> At 02/27/2012 11:08 PM, Jan Kiszka Wrote:
>>>>>>>> On 2012-02-27 04:01, Wen Congyang wrote:
>>>>>>>>> We can know the guest is paniced when the guest runs on xen.
>>>>>>>>> But we do not have such feature on kvm. This patch implemnts
>>>>>>>>> this feature, and the implementation is the same as xen:
>>>>>>>>> register panic notifier, and call hypercall when the guest
>>>>>>>>> is paniced.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Wen Congyang <wency@...fujitsu.com>
>>>>>>>>> ---
>>>>>>>>> arch/x86/kernel/kvm.c | 12 ++++++++++++
>>>>>>>>> arch/x86/kvm/svm.c | 8 ++++++--
>>>>>>>>> arch/x86/kvm/vmx.c | 8 ++++++--
>>>>>>>>> arch/x86/kvm/x86.c | 13 +++++++++++--
>>>>>>>>> include/linux/kvm.h | 1 +
>>>>>>>>> include/linux/kvm_para.h | 1 +
>>>>>>>>> 6 files changed, 37 insertions(+), 6 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>>>>>>>>> index f0c6fd6..b928d1d 100644
>>>>>>>>> --- a/arch/x86/kernel/kvm.c
>>>>>>>>> +++ b/arch/x86/kernel/kvm.c
>>>>>>>>> @@ -331,6 +331,17 @@ 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_hypercall0(KVM_HC_GUEST_PANIC);
>>>>>>>>> + return NOTIFY_DONE;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static struct notifier_block kvm_pv_panic_nb = {
>>>>>>>>> + .notifier_call = kvm_pv_panic_notify,
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>
>>>>>>>> You should split up host and guest-side changes.
>>>>>>>>
>>>>>>>>> static u64 kvm_steal_clock(int cpu)
>>>>>>>>> {
>>>>>>>>> u64 steal;
>>>>>>>>> @@ -417,6 +428,7 @@ void __init kvm_guest_init(void)
>>>>>>>>>
>>>>>>>>> paravirt_ops_setup();
>>>>>>>>> register_reboot_notifier(&kvm_pv_reboot_nb);
>>>>>>>>> + 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/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>>>>>>>>> index 0b7690e..38b4705 100644
>>>>>>>>> --- a/arch/x86/kvm/svm.c
>>>>>>>>> +++ b/arch/x86/kvm/svm.c
>>>>>>>>> @@ -1900,10 +1900,14 @@ static int halt_interception(struct vcpu_svm *svm)
>>>>>>>>>
>>>>>>>>> static int vmmcall_interception(struct vcpu_svm *svm)
>>>>>>>>> {
>>>>>>>>> + int ret;
>>>>>>>>> +
>>>>>>>>> svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
>>>>>>>>> skip_emulated_instruction(&svm->vcpu);
>>>>>>>>> - kvm_emulate_hypercall(&svm->vcpu);
>>>>>>>>> - return 1;
>>>>>>>>> + ret = kvm_emulate_hypercall(&svm->vcpu);
>>>>>>>>> +
>>>>>>>>> + /* Ignore the error? */
>>>>>>>>> + return ret == 0 ? 0 : 1;
>>>>>>>>
>>>>>>>> Why can't kvm_emulate_hypercall return the right value?
>>>>>>>
>>>>>>> kvm_emulate_hypercall() will call kvm_hv_hypercall(), and
>>>>>>> kvm_hv_hypercall() will return 0 when vcpu's CPL > 0.
>>>>>>> If vcpu's CPL > 0, does kvm need to exit and tell it to
>>>>>>> qemu?
>>>>>>
>>>>>> No, there is currently no exit to userspace due to hypercalls, neither
>>>>>> of HV nor KVM kind.
>>>>>>
>>>>>> The point is that the return code of kvm_emulate_hypercall is unused so
>>>>>> far, so you can easily redefine it to encode continue vs. exit to
>>>>>> userspace. Once someone has different needs, this could still be
>>>>>> refactored again.
>>>>>
>>>>> So, it is OK to change the return value of kvm_hv_hypercall() if vcpu's
>>>>> CPL > 0?
>>>>
>>>> Yes, change it to encode what vendor modules need to return to their
>>>> callers.
>>>>
>>> Better introduce new request flag and set it in your hypercall emulation. See
>>> how triple fault is handled.
>>
>> triple fault sets KVM_EXIT_SHUTDOWN and exits to userspace. Do you mean introduce
>> a new value(like KVM_EXIT_SHUTDOWN)?
>>
> I mean introduce new request bit (like KVM_REQ_TRIPLE_FAULT) and set it
> in your hypercall if exit to userspace is needed instead of changing
> return values.
I donot notice it. Thanks for you suggestion. I will modify my patch.
Thanks
Wen Congyang
>
> --
> Gleb.
>
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