Re: [PATCH v1] x86: make Viridian support optional

[Jan Beulich <jbeulich@xxxxxxxx>]

On 17.03.2025 10:19, Alejandro Vallejo wrote:
> Hi,
> 
> I'm surprised this isn't already possible. Neat!
> 
> On Mon, 17 Mar 2025, 07:19 Sergiy Kibrik, <Sergiy_Kibrik@xxxxxxxx> wrote:
> 
>> Add config option HVM_VIRIDIAN that covers viridian code within HVM.
>> Calls to viridian functions guarded by is_viridian_domain() and related
>> macros.
>> Having this option may be beneficial by reducing code footprint for systems
>> that are not using Hyper-V.
>>
>> Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
>> ---
>>  xen/arch/x86/Kconfig                  |  5 +++++
>>  xen/arch/x86/hvm/Makefile             |  2 +-
>>  xen/arch/x86/hvm/hvm.c                | 27 ++++++++++++++++++---------
>>  xen/arch/x86/hvm/vlapic.c             | 11 +++++++----
>>  xen/arch/x86/include/asm/hvm/domain.h |  4 ++--
>>  xen/arch/x86/include/asm/hvm/hvm.h    |  3 ++-
>>  xen/arch/x86/include/asm/hvm/vcpu.h   |  3 ++-
>>  7 files changed, 37 insertions(+), 18 deletions(-)
>>
>> diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
>> index 6e41bc0fb4..34f9b79d98 100644
>> --- a/xen/arch/x86/Kconfig
>> +++ b/xen/arch/x86/Kconfig
>> @@ -348,6 +348,11 @@ config HYPERV_GUEST
>>
>>  endif
>>
>> +config HVM_VIRIDIAN
>> +       bool "Viridian enlightenments support" if EXPERT
>> +       depends on HVM
>> +       default y
>> +
>>
> 
> 
> I don't see why this should be gated by EXPERT, provided a
> suitable (now absent) help message was to exist explaining
> what it does in plain simple words.
> 
> For the title, I'd say it needs to properly state it refers to
> enlightenments for guests, rather than enlightenments for
> Xen itself when running under Hyper-V. As it is, it sounds
> ambiguous (Maybe "Hyper-V enlighnments for guests"?).

I'm slightly puzzled: Here you're worried about ambiguity, yet then ...

> On a personal nitpicky preference note, I'd say HVM_VIRIDIAN sounds
> rather redundant, and I think just VIRIDIAN works just as well
> while being shorter.

... you suggest to introduce ambiguity here. I'd expect VIRIDIAN alone
to cover whatever enlightenments Xen might want to use itself, when
run on top of Viridian.

Jan