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Re: [PATCH v5] x86: make Viridian support optional
- To: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>, Grygorii Strashko <grygorii_strashko@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 13 Oct 2025 13:06:57 +0200
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- Cc: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 13 Oct 2025 11:07:08 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 13.10.2025 12:01, Alejandro Vallejo wrote:
> On Wed Oct 8, 2025 at 6:04 PM CEST, 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?
>
> Hypervisor-assisted IPIs, TLB flushes, etc. Or so I understood back when I
> said
> that looked ok.
Just to clarify my take: IPIs fall under "interrupt handling", and TLB flushes
to me fall under memory management, not I/O.
> I see there could be confusion with Xen PV device protocols,
> but as far as the user of the help message is concerned it makes no
> difference.
Does it not? To me it does.
> One could even remove the examples and leave it as "... for Hyper-V guests.
> This
> is to...". They are truly inconsequential.
>
> All that matters is that (modern) Windows won't run without it, and that it
> provides some indeterminate hypervisor-provided assists to try to reduce some
> virtualization overheads.
I think I'm happy for the other examples to stay, as they provide some extra
context for less aware users.
Jan
|
