Re: [PATCH] kvm: notify host when guest paniced

[Wen Congyang <wency@cn.fujitsu.com>]

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@cn.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?

Thanks
Wen Congyang

> 
>>  }
>>  
>>  static unsigned long nested_svm_get_tdp_cr3(struct kvm_vcpu *vcpu)
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 66147ca..1b57ebb 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -4582,9 +4582,13 @@ static int handle_halt(struct kvm_vcpu *vcpu)
>>  
>>  static int handle_vmcall(struct kvm_vcpu *vcpu)
>>  {
>> +	int ret;
>> +
>>  	skip_emulated_instruction(vcpu);
>> -	kvm_emulate_hypercall(vcpu);
>> -	return 1;
>> +	ret = kvm_emulate_hypercall(vcpu);
>> +
>> +	/* Ignore the error? */
>> +	return ret == 0 ? 0 : 1;
>>  }
>>  
>>  static int handle_invd(struct kvm_vcpu *vcpu)
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index c9d99e5..3fc2853 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -4923,7 +4923,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>>  	u64 param, ingpa, outgpa, ret;
>>  	uint16_t code, rep_idx, rep_cnt, res = HV_STATUS_SUCCESS, rep_done = 0;
>>  	bool fast, longmode;
>> -	int cs_db, cs_l;
>> +	int cs_db, cs_l, r = 1;
>>  
>>  	/*
>>  	 * hypercall generates UD from non zero cpl and real mode
>> @@ -4964,6 +4964,10 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>>  	case HV_X64_HV_NOTIFY_LONG_SPIN_WAIT:
>>  		kvm_vcpu_on_spin(vcpu);
>>  		break;
>> +	case KVM_HC_GUEST_PANIC:
>> +		vcpu->run->exit_reason = KVM_EXIT_GUEST_PANIC;
>> +		r = 0;
>> +		break;
> 
> That's the wrong place. This is a KVM hypercall, not a HyperV one.
> 
>>  	default:
>>  		res = HV_STATUS_INVALID_HYPERCALL_CODE;
>>  		break;
>> @@ -4977,7 +4981,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>>  		kvm_register_write(vcpu, VCPU_REGS_RAX, ret & 0xffffffff);
>>  	}
>>  
>> -	return 1;
>> +	return r;
>>  }
>>  
>>  int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>> @@ -5013,6 +5017,11 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>>  	case KVM_HC_VAPIC_POLL_IRQ:
>>  		ret = 0;
>>  		break;
>> +	case KVM_HC_GUEST_PANIC:
>> +		ret = 0;
>> +		vcpu->run->exit_reason = KVM_EXIT_GUEST_PANIC;
>> +		r = 0;
>> +		break;
>>  	default:
>>  		ret = -KVM_ENOSYS;
>>  		break;
>> diff --git a/include/linux/kvm.h b/include/linux/kvm.h
>> index acbe429..8f0e31b 100644
>> --- a/include/linux/kvm.h
>> +++ b/include/linux/kvm.h
>> @@ -163,6 +163,7 @@ struct kvm_pit_config {
>>  #define KVM_EXIT_OSI              18
>>  #define KVM_EXIT_PAPR_HCALL	  19
>>  #define KVM_EXIT_S390_UCONTROL	  20
>> +#define KVM_EXIT_GUEST_PANIC	  21
>>  
>>  /* For KVM_EXIT_INTERNAL_ERROR */
>>  #define KVM_INTERNAL_ERROR_EMULATION 1
>> diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
>> index ff476dd..cf94023 100644
>> --- a/include/linux/kvm_para.h
>> +++ b/include/linux/kvm_para.h
>> @@ -19,6 +19,7 @@
>>  #define KVM_HC_MMU_OP			2
>>  #define KVM_HC_FEATURES			3
>>  #define KVM_HC_PPC_MAP_MAGIC_PAGE	4
>> +#define KVM_HC_GUEST_PANIC		5
>>  
>>  /*
>>   * hypercalls use architecture specific
> 
> Jan
>