Re: [PATCH] vmbus: Print a warning when enabled without the recommended set of features

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

On 1/25/24 17:19, Maciej S. Szmigiero wrote:
> From: "Maciej S. Szmigiero" <maciej.szmigiero@xxxxxxxxxx>
>
> Some Windows versions crash at boot or fail to enable the VMBus device if
> they don't see the expected set of Hyper-V features (enlightenments).
>
> Since this provides poor user experience let's warn user if the VMBus
> device is enabled without the recommended set of Hyper-V features.
>
> The recommended set is the minimum set of Hyper-V features required to make
> the VMBus device work properly in Windows Server versions 2016, 2019 and
> 2022.
>
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@xxxxxxxxxx>

Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Thanks,

Paolo

> ---
>   hw/hyperv/hyperv.c            | 12 ++++++++++++
>   hw/hyperv/vmbus.c             |  6 ++++++
>   include/hw/hyperv/hyperv.h    |  4 ++++
>   target/i386/kvm/hyperv-stub.c |  4 ++++
>   target/i386/kvm/hyperv.c      |  5 +++++
>   target/i386/kvm/hyperv.h      |  2 ++
>   target/i386/kvm/kvm.c         |  7 +++++++
>   7 files changed, 40 insertions(+)
>
> diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
> index 57b402b95610..2c91de7ff4a8 100644
> --- a/hw/hyperv/hyperv.c
> +++ b/hw/hyperv/hyperv.c
> @@ -947,3 +947,15 @@ uint64_t hyperv_syndbg_query_options(void)
>   
>       return msg.u.query_options.options;
>   }
> +
> +static bool vmbus_recommended_features_enabled;
> +
> +bool hyperv_are_vmbus_recommended_features_enabled(void)
> +{
> +    return vmbus_recommended_features_enabled;
> +}
> +
> +void hyperv_set_vmbus_recommended_features_enabled(void)
> +{
> +    vmbus_recommended_features_enabled = true;
> +}
> diff --git a/hw/hyperv/vmbus.c b/hw/hyperv/vmbus.c
> index 380239af2c7b..f33afeeea27d 100644
> --- a/hw/hyperv/vmbus.c
> +++ b/hw/hyperv/vmbus.c
> @@ -2631,6 +2631,12 @@ static void vmbus_bridge_realize(DeviceState *dev, Error **errp)
>           return;
>       }
>   
> +    if (!hyperv_are_vmbus_recommended_features_enabled()) {
> +        warn_report("VMBus enabled without the recommended set of Hyper-V features: "
> +                    "hv-stimer, hv-vapic and hv-runtime. "
> +                    "Some Windows versions might not boot or enable the VMBus device");
> +    }
> +
>       bridge->bus = VMBUS(qbus_new(TYPE_VMBUS, dev, "vmbus"));
>   }
>   
> diff --git a/include/hw/hyperv/hyperv.h b/include/hw/hyperv/hyperv.h
> index 015c3524b1c2..d717b4e13d40 100644
> --- a/include/hw/hyperv/hyperv.h
> +++ b/include/hw/hyperv/hyperv.h
> @@ -139,4 +139,8 @@ typedef struct HvSynDbgMsg {
>   } HvSynDbgMsg;
>   typedef uint16_t (*HvSynDbgHandler)(void *context, HvSynDbgMsg *msg);
>   void hyperv_set_syndbg_handler(HvSynDbgHandler handler, void *context);
> +
> +bool hyperv_are_vmbus_recommended_features_enabled(void);
> +void hyperv_set_vmbus_recommended_features_enabled(void);
> +
>   #endif
> diff --git a/target/i386/kvm/hyperv-stub.c b/target/i386/kvm/hyperv-stub.c
> index 778ed782e6fc..3263dcf05d31 100644
> --- a/target/i386/kvm/hyperv-stub.c
> +++ b/target/i386/kvm/hyperv-stub.c
> @@ -52,3 +52,7 @@ void hyperv_x86_synic_reset(X86CPU *cpu)
>   void hyperv_x86_synic_update(X86CPU *cpu)
>   {
>   }
> +
> +void hyperv_x86_set_vmbus_recommended_features_enabled(void)
> +{
> +}
> diff --git a/target/i386/kvm/hyperv.c b/target/i386/kvm/hyperv.c
> index 6825c89af374..f2a3fe650a18 100644
> --- a/target/i386/kvm/hyperv.c
> +++ b/target/i386/kvm/hyperv.c
> @@ -149,3 +149,8 @@ int kvm_hv_handle_exit(X86CPU *cpu, struct kvm_hyperv_exit *exit)
>           return -1;
>       }
>   }
> +
> +void hyperv_x86_set_vmbus_recommended_features_enabled(void)
> +{
> +    hyperv_set_vmbus_recommended_features_enabled();
> +}
> diff --git a/target/i386/kvm/hyperv.h b/target/i386/kvm/hyperv.h
> index 67543296c3a4..e3982c8f4dd1 100644
> --- a/target/i386/kvm/hyperv.h
> +++ b/target/i386/kvm/hyperv.h
> @@ -26,4 +26,6 @@ int hyperv_x86_synic_add(X86CPU *cpu);
>   void hyperv_x86_synic_reset(X86CPU *cpu);
>   void hyperv_x86_synic_update(X86CPU *cpu);
>   
> +void hyperv_x86_set_vmbus_recommended_features_enabled(void);
> +
>   #endif
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index e88e65fe014c..d3d01b3cf82d 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -1650,6 +1650,13 @@ static int hyperv_init_vcpu(X86CPU *cpu)
>           }
>       }
>   
> +    /* Skip SynIC and VP_INDEX since they are hard deps already */
> +    if (hyperv_feat_enabled(cpu, HYPERV_FEAT_STIMER) &&
> +        hyperv_feat_enabled(cpu, HYPERV_FEAT_VAPIC) &&
> +        hyperv_feat_enabled(cpu, HYPERV_FEAT_RUNTIME)) {
> +        hyperv_x86_set_vmbus_recommended_features_enabled();
> +    }
> +
>       return 0;
>   }
>