On 09.10.2025 18:33, Grygorii Strashko wrote:
> On 08.10.25 19:04, Jan Beulich wrote:
>> On 30.09.2025 14:52, 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 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.
>>
>> What is "paravirtualized I/O" about in this context?
>
> It was phrased this way and agreed upon from the very beginning [1]
>
> [1]
> https://patchwork.kernel.org/project/xen-devel/patch/[email protected]/#26305207
Hmm, I'm not sure I would call this "agreed upon". Plus this doesn't answer
my question.
>>> --- a/xen/arch/x86/hvm/hvm.c
>>> +++ b/xen/arch/x86/hvm/hvm.c
>>> @@ -701,9 +701,12 @@ int hvm_domain_initialise(struct domain *d,
>>> if ( hvm_tsc_scaling_supported )
>>> d->arch.hvm.tsc_scaling_ratio = hvm_default_tsc_scaling_ratio;
>>> - rc = viridian_domain_init(d);
>>> - if ( rc )
>>> - goto fail2;
>>> + if ( is_viridian_domain(d) )
>>> + {
>>> + rc = viridian_domain_init(d);
>>> + if ( rc )
>>> + goto fail2;
>>> + }
>>
>> While this looks okay to me, ...
>>
>>> @@ -739,7 +742,8 @@ void hvm_domain_relinquish_resources(struct domain *d)
>>> if ( hvm_funcs.nhvm_domain_relinquish_resources )
>>> alternative_vcall(hvm_funcs.nhvm_domain_relinquish_resources, d);
>>> - viridian_domain_deinit(d);
>>> + if ( is_viridian_domain(d) )
>>> + viridian_domain_deinit(d);
>>
>> ... I wonder if viridian_{domain,vcpu}_deinit() better wouldn't be tolerant
>> to be called anyway, thus avoiding the need for conditionals here and below
>> (and perhaps being a little more robust overall). Thoughts?
>
> I think There are no limits for perfection. But at some point - need to stop.
>
> Hence Viridian code will be removed from build when !VIRIDIAN - changing
> above code will
> require to add stubs for viridian_{domain,vcpu}_deinit().
Fair point.
Jan
