Re: [Qemu-devel] [PATCH 07/11] kvm/x86: added hyper-v crash data and ctl msr's get/set'ers

[Peter Hornyack]

On Mon, Jun 22, 2015 at 9:05 AM, Denis V. Lunev <address@hidden> wrote:
> From: Andrey Smetanin <address@hidden>
>
> Added hyper-v crash msr's(HV_X64_MSR_CRASH*) data and control
> geters and setters.
>
> Signed-off-by: Andrey Smetanin <address@hidden>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: Paolo Bonzini <address@hidden>
> CC: Gleb Natapov <address@hidden>
> ---
>  arch/x86/kvm/hyperv.c | 66 
> +++++++++++++++++++++++++++++++++++++++++++++++++++
>  arch/x86/kvm/x86.c    |  4 ++++
>  2 files changed, 70 insertions(+)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index f65fb622..0a7d373 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -46,6 +46,59 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
>         return r;
>  }
>
> +static int kvm_hv_msr_get_crash_ctl(struct kvm_vcpu *vcpu, u64 *pdata)
> +{
> +       struct kvm_arch_hyperv *hv = &vcpu->kvm->arch.hyperv;
> +
> +       *pdata = hv->hv_crash_ctl;

I see that this is implemented so that userspace controls the Hyper-V
crash capabilities that are enabled - userspace must set
HV_X64_MSR_CRASH_CTL_NOTIFY before the guest reads
HV_X64_MSR_CRASH_CTL. I just want to check that you considered an
alternative: a simpler implementation would have the crash
capabilities statically defined by kvm, and
HV_X64_MSR_CRASH_CTL_CONTENTS could just be returned here (and
hv_crash_ctl could be removed from struct kvm_arch_hyperv).

The current implementation is potentially more flexible but makes the
MSR handling a little more awkward since the host_initiated bool needs
to be passed around (patch 09). I guess either approach seems ok to
me.

Also, if this patchset is used then it looks like
HV_X64_MSR_CRASH_CTL_CONTENTS can be removed.

> +       return 0;
> +}
> +
> +static int kvm_hv_msr_set_crash_ctl(struct kvm_vcpu *vcpu, u64 data)
> +{
> +       struct kvm_arch_hyperv *hv = &vcpu->kvm->arch.hyperv;
> +
> +       hv->hv_crash_ctl = data;
> +       if ((data & HV_X64_MSR_CRASH_CTL_NOTIFY)) {
> +               vcpu_debug(vcpu, "hv crash (0x%llx 0x%llx 0x%llx 0x%llx "
> +                         "0x%llx)\n", hv->hv_crash_param[0],
> +                         hv->hv_crash_param[1],
> +                         hv->hv_crash_param[2],
> +                         hv->hv_crash_param[3],
> +                         hv->hv_crash_param[4]);
> +
> +               /* Send notification about crash to user space */
> +               kvm_make_request(KVM_REQ_HV_CRASH, vcpu);
> +               return 0;

Returning from here seems unnecessary - if more crash capabilities are
added in the future, the guest might want to invoke multiple
capabilities at once, so we'd want to check for those here too.

> +       }
> +
> +       return 0;
> +}
> +
> +static int kvm_hv_msr_set_crash_data(struct kvm_vcpu *vcpu,
> +                                    u32 index, u64 data)
> +{
> +       struct kvm_arch_hyperv *hv = &vcpu->kvm->arch.hyperv;
> +
> +       if (WARN_ON_ONCE(index >= ARRAY_SIZE(hv->hv_crash_param)))
> +               return -EINVAL;
> +
> +       hv->hv_crash_param[index] = data;
> +       return 0;
> +}
> +
> +static int kvm_hv_msr_get_crash_data(struct kvm_vcpu *vcpu,
> +                                    u32 index, u64 *pdata)
> +{
> +       struct kvm_arch_hyperv *hv = &vcpu->kvm->arch.hyperv;
> +
> +       if (WARN_ON_ONCE(index >= ARRAY_SIZE(hv->hv_crash_param)))
> +               return -EINVAL;
> +
> +       *pdata = hv->hv_crash_param[index];
> +       return 0;
> +}
> +
>  static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  {
>         struct kvm *kvm = vcpu->kvm;
> @@ -98,6 +152,12 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 
> msr, u64 data)
>                 mark_page_dirty(kvm, gfn);
>                 break;
>         }
> +       case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
> +               return kvm_hv_msr_set_crash_data(vcpu,
> +                                                msr - HV_X64_MSR_CRASH_P0,
> +                                                data);
> +       case HV_X64_MSR_CRASH_CTL:
> +               return kvm_hv_msr_set_crash_ctl(vcpu, data);
>         default:
>                 vcpu_unimpl(vcpu, "Hyper-V unimpl wrmsr: 0x%x data 0x%llx\n",
>                                   msr, data);
> @@ -170,6 +230,12 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 
> msr, u64 *pdata)
>         case HV_X64_MSR_REFERENCE_TSC:
>                 data = hv->hv_tsc_page;
>                 break;
> +       case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
> +               return kvm_hv_msr_get_crash_data(vcpu,
> +                                                msr - HV_X64_MSR_CRASH_P0,
> +                                                pdata);
> +       case HV_X64_MSR_CRASH_CTL:
> +               return kvm_hv_msr_get_crash_ctl(vcpu, pdata);
>         default:
>                 vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
>                 return 1;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2755c37..2046b78 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2208,6 +2208,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct 
> msr_data *msr_info)
>                  */
>                 break;
>         case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
> +       case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
> +       case HV_X64_MSR_CRASH_CTL:
>                 return kvm_hv_set_msr_common(vcpu, msr, data);
>                 break;
>         case MSR_IA32_BBL_CR_CTL3:
> @@ -2451,6 +2453,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, 
> u64 *pdata)
>                 data = 0x20000000;
>                 break;
>         case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
> +       case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
> +       case HV_X64_MSR_CRASH_CTL:
>                 return kvm_hv_get_msr_common(vcpu, msr, pdata);
>                 break;
>         case MSR_IA32_BBL_CR_CTL3:
> --
> 1.9.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in