Re: [Qemu-devel] [PATCH] kvm: notify host when guest paniced

[Jan Kiszka]

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 <address@hidden>
> ---
>  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?

>  }
>  
>  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

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