# Re: \[PATCH V3 03/13\] x86/HV: Add new hvcall guest address host visibility support

- From: Tianyu Lan \<hidden\>
- Date: 2021-08-10 13:09:35 
- List: netdev
- Page: https://ratatoskr.run/netdev/2021/08/1473097
- Thread: https://ratatoskr.run/xen-devel/2021/08/1472230/t.md

```text
On 8/10/2021 6:12 AM, Dave Hansen wrote:
> On 8/9/21 10:56 AM, Tianyu Lan wrote:
>> From: Tianyu Lan <redacted>
>>
>> Add new hvcall guest address host visibility support to mark
>> memory visible to host. Call it inside set_memory_decrypted
>> /encrypted(). Add HYPERVISOR feature check in the
>> hv_is_isolation_supported() to optimize in non-virtualization
>> environment.
>
>  From an x86/mm perspective:
>
> Acked-by: Dave Hansen <redacted>
>

Thanks for your ACK.


> A tiny nit:
>
>> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
>> index 0bb4d9ca7a55..b3683083208a 100644
>> --- a/arch/x86/hyperv/hv_init.c
>> +++ b/arch/x86/hyperv/hv_init.c
>> @@ -607,6 +607,12 @@ EXPORT_SYMBOL_GPL(hv_get_isolation_type);
>>   
>>   bool hv_is_isolation_supported(void)
>>   {
>> +	if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
>> +		return 0;
>> +
>> +	if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
>> +		return 0;
>> +
>>   	return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
>>   }
> This might be worthwhile to move to a header.  That ensures that
> hv_is_isolation_supported() use can avoid even a function call.  But, I
> see this is used in modules and its use here is also in a slow path, so
> it's not a big deal
>

I will move it to header in the following version.


Thanks.
```