Re: [PATCH 06/12] target/i386/mshv: migrate Synic SINT MSRs

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

On Fri, Jul 10, 2026 at 12:15:28PM +0200, Magnus Kulke wrote:
> Migrate HyperV SynIC SINT MSRs. We can only read/write those if SCONTROL
> is enabled in the guest, hence we have to split the SINT MSR out and
> make reading/writing them dependent on that MSR.
> 
> Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
> ---
>  target/i386/mshv/msr.c | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/target/i386/mshv/msr.c b/target/i386/mshv/msr.c
> index a5f639c3ca..5288e32b6d 100644
> --- a/target/i386/mshv/msr.c
> +++ b/target/i386/mshv/msr.c
> @@ -331,6 +331,8 @@ int mshv_get_msrs(CPUState *cpu)
>      struct hv_register_assoc assocs[MSHV_MSR_TOTAL_COUNT];
>      size_t i, j;
>      uint32_t name;
> +    X86CPU *x86cpu = X86_CPU(cpu);
> +    bool synic_enabled;
>  
>      set_hv_name_in_assocs(assocs, n_assocs);
>  
> @@ -357,6 +359,27 @@ int mshv_get_msrs(CPUState *cpu)
>  
>      store_in_env(cpu, assocs, n_assocs);
>  
> +    /* Read SINT MSRs only if SynIC is enabled */
> +    synic_enabled = x86cpu->env.msr_hv_synic_control & 1;
> +    if (synic_enabled) {
> +        QEMU_BUILD_BUG_ON(MSHV_MSR_TOTAL_COUNT < HV_SINT_COUNT);
> +
> +        for (i = 0; i < HV_SINT_COUNT; i++) {
> +            assocs[i].name = HV_REGISTER_SINT0 + i;
> +        }
> +
> +        ret = mshv_get_generic_regs(cpu, assocs, HV_SINT_COUNT);
> +        if (ret < 0) {
> +            error_report("Failed to get SynIC SINT MSRs");
> +            return -errno;
> +        }
> +
> +        for (i = 0; i < HV_SINT_COUNT; i++) {
> +            uint64_t hv_sint_value = assocs[i].value.reg64;
> +            x86cpu->env.msr_hv_synic_sint[i] = hv_sint_value;
> +        }
> +    }
> +
>      return 0;
>  }
>  
> @@ -391,6 +414,8 @@ int mshv_set_msrs(const CPUState *cpu)
>      struct hv_register_assoc assocs[MSHV_MSR_TOTAL_COUNT];
>      int ret;
>      size_t i, j;
> +    X86CPU *x86cpu = X86_CPU(cpu);
> +    bool synic_enabled = x86cpu->env.msr_hv_synic_control & 1;
>  
>      load_from_env(cpu, assocs, n_assocs);
>  
> @@ -423,5 +448,21 @@ int mshv_set_msrs(const CPUState *cpu)
>          return -errno;
>      }
>  
> +    /* SINT MSRs can only be written if SCONTROL has been set, so we split */
> +    if (synic_enabled) {
> +        QEMU_BUILD_BUG_ON(MSHV_MSR_TOTAL_COUNT < HV_SINT_COUNT);
> +
> +        for (i = 0; i < HV_SINT_COUNT; i++) {
> +            assocs[i].name        = HV_REGISTER_SINT0 + i;
> +            assocs[i].value.reg64 = x86cpu->env.msr_hv_synic_sint[i];
> +        }
> +
> +        ret = mshv_set_generic_regs(cpu, assocs, HV_SINT_COUNT);
> +        if (ret < 0) {
> +            error_report("Failed to set SynIC SINT MSRs");
> +            return -errno;
> +        }
> +    }
> +
>      return 0;
>  }
> -- 
> 2.34.1

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