Re: [PATCH 09/12] accel/mshv: write synthetic MSRs after migration

["Doru Blânzeanu" <dblanzeanu@linux.microsoft.com>]

On Fri, Jul 10, 2026 at 12:15:31PM +0200, Magnus Kulke wrote:
> Write partition-wide synthetic MSRs. This ensures the hypercall page and
> SynIC facilities are set up before vCPUs attempt to use it.
> 
> Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
> ---
>  accel/mshv/mshv-all.c          | 15 +++++++++++++++
>  include/hw/hyperv/hvgdk_mini.h |  3 +++
>  include/system/mshv_int.h      |  1 +
>  target/i386/mshv/mshv-cpu.c    | 15 +++++++++++++++
>  4 files changed, 34 insertions(+)
> 
> diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
> index 1516475f34..1ca1d4b54f 100644
> --- a/accel/mshv/mshv-all.c
> +++ b/accel/mshv/mshv-all.c
> @@ -60,6 +60,20 @@ static int init_mshv(int *mshv_fd)
>      return 0;
>  }
>  
> +static int mshv_load_cleanup(void *opaque)
> +{
> +    int ret;
> +
> +    ret = mshv_arch_set_partition_msrs(first_cpu);
> +    if (ret < 0) {
> +        error_report("Failed to set partition MSRs: %s", strerror(-ret));
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +
>  static int get_host_partition_property(int mshv_fd, uint32_t property_code,
>                                         uint64_t *value)
>  {
> @@ -496,6 +510,7 @@ static int mshv_init_vcpu(CPUState *cpu)
>  }
>  
>  static SaveVMHandlers savevm_mshv = {
> +    .load_cleanup = mshv_load_cleanup,
>  };
>  
>  static int mshv_init(AccelState *as, MachineState *ms)
> diff --git a/include/hw/hyperv/hvgdk_mini.h b/include/hw/hyperv/hvgdk_mini.h
> index 0602a7c6cc..a5527d49cf 100644
> --- a/include/hw/hyperv/hvgdk_mini.h
> +++ b/include/hw/hyperv/hvgdk_mini.h
> @@ -23,6 +23,9 @@
>  #define HV_X64_MSR_APIC_FREQUENCY   0x40000023
>  
>  typedef enum hv_register_name {
> +    /* VP Management Registers */
> +    HV_REGISTER_INTERNAL_ACTIVITY_STATE = 0x00000004,
> +
>      /* Pending Interruption Register */
>      HV_REGISTER_PENDING_INTERRUPTION = 0x00010002,
>      HV_REGISTER_INTERRUPT_STATE      = 0x00010003,
> diff --git a/include/system/mshv_int.h b/include/system/mshv_int.h
> index 063852115e..cbfcb8611b 100644
> --- a/include/system/mshv_int.h
> +++ b/include/system/mshv_int.h
> @@ -98,6 +98,7 @@ int mshv_get_generic_regs(CPUState *cpu, hv_register_assoc *assocs,
>                            size_t n_regs);
>  int mshv_arch_store_vcpu_state(const CPUState *cpu);
>  int mshv_arch_load_vcpu_state(CPUState *cpu);
> +int mshv_arch_set_partition_msrs(const CPUState *cpu);
>  void mshv_arch_init_vcpu(CPUState *cpu);
>  void mshv_arch_destroy_vcpu(CPUState *cpu);
>  void mshv_arch_amend_proc_features(
> diff --git a/target/i386/mshv/mshv-cpu.c b/target/i386/mshv/mshv-cpu.c
> index ce6cfccc0a..1485f6a1ef 100644
> --- a/target/i386/mshv/mshv-cpu.c
> +++ b/target/i386/mshv/mshv-cpu.c
> @@ -1505,6 +1505,21 @@ int mshv_arch_store_vcpu_state(const CPUState *cpu)
>      return 0;
>  }
>  
> +int mshv_arch_set_partition_msrs(const CPUState *cpu)
> +{
> +    CPUX86State *env = &X86_CPU(cpu)->env;
> +    struct hv_register_assoc assocs[] = {
> +        { .name = HV_REGISTER_GUEST_OS_ID,
> +          .value.reg64 = env->msr_hv_guest_os_id },
> +        { .name = HV_REGISTER_REFERENCE_TSC,
> +          .value.reg64 = env->msr_hv_tsc },
> +        { .name = HV_X64_REGISTER_HYPERCALL,
> +          .value.reg64 = env->msr_hv_hypercall },
> +    };
> +
> +    return mshv_set_generic_regs(cpu, assocs, ARRAY_SIZE(assocs));
> +}
> +
>  void mshv_arch_amend_proc_features(
>      union hv_partition_synthetic_processor_features *features)
>  {
> -- 
> 2.34.1

Reviewed-by: Doru Blânzeanu <dblanzeanu@linux.microsoft.com>