Re: [XEN][PATCH v3] x86: make Viridian support optional

[Jan Beulich <jbeulich@xxxxxxxx>]

On 18.09.2025 17:15, Grygorii Strashko wrote:
> On 16.09.25 16:41, Grygorii Strashko wrote:
>> --- a/xen/arch/x86/hvm/Kconfig
>> +++ b/xen/arch/x86/hvm/Kconfig
>> @@ -62,6 +62,16 @@ config ALTP2M
>>   
>>        If unsure, stay with defaults.
>>   
>> +config HVM_VIRIDIAN
>> +    bool "Hyper-V enlightenments for guests" if EXPERT
>> +    default y
>> +    help
>> +      Support optimizations for Hyper-V guests such as faster hypercalls,
>> +      efficient timer and interrupt handling, and enhanced paravirtualized
>> +      I/O. This is to improve performance and compatibility of Windows VMs.
>> +
>> +      If unsure, say Y.
>> +
> 
> Actually there is a question for x86 Experts -
> Does it make sense to have HVM_VIRIDIAN enabled without enabled 
> AMD_SVM/INTEL_VMX Virtualization extensions?

It makes as much or as little sense as HVM=y with both of the ones you mention
turned off. Iirc Andrew in particular wanted to permit such configurations, to
allow to prove the (abstract) correctness of building them, even if the
resulting hypervisor may be of little use.

Jan