Re: [PATCH 10/12] target/i386/mshv: migrate MP_STATE

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

On Fri, Jul 10, 2026 at 12:15:32PM +0200, Magnus Kulke wrote:
> MSHV's "internal activity state" roughly maps to QEMU's env->mp_state
> and cpu->halted states that describe state of APs in a guest.
> 
> We don't invoke set_mp_state as part of store_vcpu_state() b/c we would
> put all BSP + APs in a RUNNABLE (0) state immediately, breaking SMP boot
> 
> Instead we store the mp state as part of the load_cleanup() routine
> after a migration.
> 
> Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
> ---
>  accel/mshv/mshv-all.c       | 10 +++++
>  include/system/mshv_int.h   |  1 +
>  target/i386/mshv/mshv-cpu.c | 80 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 91 insertions(+)
> 
> diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
> index 1ca1d4b54f..5921ce693e 100644
> --- a/accel/mshv/mshv-all.c
> +++ b/accel/mshv/mshv-all.c
> @@ -62,6 +62,7 @@ static int init_mshv(int *mshv_fd)
>  
>  static int mshv_load_cleanup(void *opaque)
>  {
> +    CPUState *cpu;
>      int ret;
>  
>      ret = mshv_arch_set_partition_msrs(first_cpu);
> @@ -70,6 +71,15 @@ static int mshv_load_cleanup(void *opaque)
>          return -1;
>      }
>  
> +    CPU_FOREACH(cpu) {
> +        ret = mshv_arch_set_mp_state(cpu);
> +        if (ret < 0) {
> +            error_report("Failed to set mp state for vCPU %d: %s",
> +                         cpu->cpu_index, strerror(-ret));
> +            return -1;
> +        }
> +    }
> +
>      return 0;
>  }
>  
> diff --git a/include/system/mshv_int.h b/include/system/mshv_int.h
> index cbfcb8611b..3dffe3c5fb 100644
> --- a/include/system/mshv_int.h
> +++ b/include/system/mshv_int.h
> @@ -99,6 +99,7 @@ int mshv_get_generic_regs(CPUState *cpu, hv_register_assoc *assocs,
>  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);
> +int mshv_arch_set_mp_state(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 1485f6a1ef..bff1ac9d17 100644
> --- a/target/i386/mshv/mshv-cpu.c
> +++ b/target/i386/mshv/mshv-cpu.c
> @@ -35,6 +35,11 @@
>  
>  #include <sys/ioctl.h>
>  
> +#define MSHV_MP_STATE_RUNNABLE       0
> +#define MSHV_MP_STATE_UNINITIALIZED  1
> +#define MSHV_MP_STATE_INIT_RECEIVED  2
> +#define MSHV_MP_STATE_HALTED         3
> +
>  #define MAX_REGISTER_COUNT (MAX_CONST(ARRAY_SIZE(STANDARD_REGISTER_NAMES), \
>                              MAX_CONST(ARRAY_SIZE(SPECIAL_REGISTER_NAMES), \
>                                        ARRAY_SIZE(FPU_REGISTER_NAMES))))
> @@ -950,6 +955,76 @@ static int set_vcpu_events(const CPUState *cpu)
>      return 0;
>  }
>  
> +static int get_mp_state(CPUState *cpu)
> +{
> +    X86CPU *x86cpu = X86_CPU(cpu);
> +    CPUX86State *env = &x86cpu->env;
> +    struct hv_register_assoc assoc = {
> +        .name = HV_REGISTER_INTERNAL_ACTIVITY_STATE,
> +    };
> +    union hv_internal_activity_register activity;
> +    int ret;
> +
> +    ret = mshv_get_generic_regs(cpu, &assoc, 1);
> +    if (ret < 0) {
> +        error_report("failed to get internal activity state");
> +        return -1;
> +    }
> +
> +    activity.as_uint64 = assoc.value.reg64;
> +
> +    /*
> +     * map MSHV activity state to KVM mp_state values, which are used as the
> +     * shared representation in env->mp_state and serialized by vmstate_x86_cpu.
> +     */
> +
> +    if (activity.startup_suspend) {
> +        env->mp_state = MSHV_MP_STATE_UNINITIALIZED;
> +    } else if (activity.halt_suspend) {
> +        env->mp_state = MSHV_MP_STATE_HALTED;
> +    } else {
> +        env->mp_state = MSHV_MP_STATE_RUNNABLE;
> +    }
> +
> +    cpu->halted = (env->mp_state == MSHV_MP_STATE_HALTED);
> +
> +    return 0;
> +}
> +
> +int mshv_arch_set_mp_state(const CPUState *cpu)
> +{
> +    X86CPU *x86cpu = X86_CPU(cpu);
> +    CPUX86State *env = &x86cpu->env;
> +    union hv_internal_activity_register activity = { 0 };
> +    struct hv_register_assoc assoc = {
> +        .name = HV_REGISTER_INTERNAL_ACTIVITY_STATE,
> +    };
> +    int ret;
> +
> +    switch (env->mp_state) {
> +    case MSHV_MP_STATE_HALTED:
> +        activity.halt_suspend = 1;
> +        break;
> +    case MSHV_MP_STATE_UNINITIALIZED:
> +    case MSHV_MP_STATE_INIT_RECEIVED:
> +        activity.startup_suspend = 1;
> +        break;
> +    case MSHV_MP_STATE_RUNNABLE:
> +    default:
> +        break;
> +    }
> +
> +    assoc.value.reg64 = activity.as_uint64;
> +
> +    ret = mshv_set_generic_regs(cpu, &assoc, 1);
> +    if (ret < 0) {
> +        error_report("failed to set internal activity state");
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
>  static int update_hflags(CPUState *cpu)
>  {
>      X86CPU *x86cpu = X86_CPU(cpu);
> @@ -1012,6 +1087,11 @@ int mshv_arch_load_vcpu_state(CPUState *cpu)
>          return ret;
>      }
>  
> +    ret = get_mp_state(cpu);
> +    if (ret < 0) {
> +        return ret;
> +    }
> +
>      return 0;
>  }
>  
> -- 
> 2.34.1

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