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Message-ID: <4F4D7AA4.3070801@cn.fujitsu.com>
Date: Wed, 29 Feb 2012 09:08:52 +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 02/28/2012 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)?
Thanks
Wen Congyang
>
> --
> Gleb.
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