# Re: \[PATCH V3 02/13\] x86/HV: Initialize shared memory boundary in the Isolation VM.

- From: Tianyu Lan \<hidden\>
- Date: 2021-08-14 13:33:20 
- List: linux-arch
- Page: https://ratatoskr.run/linux-arch/2021/08/1477809
- Thread: https://ratatoskr.run/xen-devel/2021/08/1472230/t.md

```text

On 8/13/2021 3:18 AM, Michael Kelley wrote:
> From: Tianyu Lan <redacted> Sent: Monday, August 9, 2021 10:56 AM
>> Subject: [PATCH V3 02/13] x86/HV: Initialize shared memory boundary in the Isolation VM.
>
> As with Patch 1, use the "x86/hyperv:" tag in the Subject line.
>
>>
>> From: Tianyu Lan <redacted>
>>
>> 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>
>> ---
>>   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 6b5835a087a3..2b7f396ef1a5 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 =
>> +			(u64)1 << ms_hyperv.shared_gpa_boundary_bits;
>
> You could use BIT_ULL() here, but it's kind of a shrug.


Good suggestion. Thanks.

>
>>
>>   		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 4269f3174e58..aa26d24a5ca9 100644
>> --- a/include/asm-generic/mshyperv.h
>> +++ b/include/asm-generic/mshyperv.h
>> @@ -35,8 +35,18 @@ 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;
>
> Any reason to name the reserved fields as "11" and "12"?  It
> just looks a bit unusual.  And I'd suggest lowercase "r".
>

Yes, will update in the next version.

>> +		};
>> +	};
>>   	void  __percpu **ghcb_base;
>> +	u64 shared_gpa_boundary;
>>   };
>>   extern struct ms_hyperv_info ms_hyperv;
>>
>> --
>> 2.25.1
>
```