# Re: \[PATCH V4 02/13\] x86/hyperv: Initialize shared memory boundary in the Isolation VM.

- From: Tianyu Lan \<hidden\>
- Date: 2021-09-02 06:35:32 
- List: netdev
- Page: https://ratatoskr.run/netdev/2021/09/1495473
- Thread: https://ratatoskr.run/xen-devel/2021/08/1490756/t.md

```text

Hi Michael:
      Thanks for your review.

On 9/2/2021 8:15 AM, Michael Kelley wrote:
> From: Tianyu Lan <redacted> Sent: Friday, August 27, 2021 10:21 AM
>>
>> Hyper-V exposes shared memory boundary via cpuid
>> HYPERV_CPUID_ISOLATION_CONFIG and store it in the
>> shared_gpa_boundary of ms_hyperv struct. This prepares
>> to share memory with host for SNP guest.
>>
>> Signed-off-by: Tianyu Lan <redacted>
>> ---
>> Change since v3:
>> 	* user BIT_ULL to get shared_gpa_boundary
>> 	* Rename field Reserved* to reserved
>> ---
>>   arch/x86/kernel/cpu/mshyperv.c |  2 ++
>>   include/asm-generic/mshyperv.h | 12 +++++++++++-
>>   2 files changed, 13 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
>> index 20557a9d6e25..8bb001198316 100644
>> --- a/arch/x86/kernel/cpu/mshyperv.c
>> +++ b/arch/x86/kernel/cpu/mshyperv.c
>> @@ -313,6 +313,8 @@ static void __init ms_hyperv_init_platform(void)
>>   	if (ms_hyperv.priv_high & HV_ISOLATION) {
>>   		ms_hyperv.isolation_config_a = cpuid_eax(HYPERV_CPUID_ISOLATION_CONFIG);
>>   		ms_hyperv.isolation_config_b = cpuid_ebx(HYPERV_CPUID_ISOLATION_CONFIG);
>> +		ms_hyperv.shared_gpa_boundary =
>> +			BIT_ULL(ms_hyperv.shared_gpa_boundary_bits);
>>
>>   		pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
>>   			ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
>> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
>> index 0924bbd8458e..7537ae1db828 100644
>> --- a/include/asm-generic/mshyperv.h
>> +++ b/include/asm-generic/mshyperv.h
>> @@ -35,7 +35,17 @@ struct ms_hyperv_info {
>>   	u32 max_vp_index;
>>   	u32 max_lp_index;
>>   	u32 isolation_config_a;
>> -	u32 isolation_config_b;
>> +	union {
>> +		u32 isolation_config_b;
>> +		struct {
>> +			u32 cvm_type : 4;
>> +			u32 reserved11 : 1;
>> +			u32 shared_gpa_boundary_active : 1;
>> +			u32 shared_gpa_boundary_bits : 6;
>> +			u32 reserved12 : 20;
>
> I'm still curious about the "11" and "12" in the reserved
> field names.  Why not just "reserved1" and "reserved2"?
> Having the "11" and "12" isn't wrong, but it makes one
> wonder why since it's not usual. :-)
>

Yes, will update. Thanks.
```