On Sat, Oct 18, 2025 at 09:21:37PM -0400, Demi Marie Obenour wrote: > On 10/17/25 11:52, Alejandro Vallejo wrote: > > On Wed Oct 15, 2025 at 7:58 AM CEST, Demi Marie Obenour wrote: > >> On 10/13/25 06:01, 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. 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. > >>> > >>> 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. > >> > >> Qubes OS doesn't expose Viridian at all, which is why it wasn't > >> vulnerable to XSA-472. It still runs Windows guests just fine. > > > > Can you run Windows 11? > > I haven't tried it, but it is documented as working. > > > I don't remember which, but I do know some versions of Windows refuse to > > boot > > if they determine they are virtualised and don't see the mandatory parts of > > the TLFS. > > > > If 11 works, maybe Windows Server? > > Windows Server is more likely.
FTR, for unrelated reasons I've tested Windows Server 2025 without Viridian, and it does work, albeit painfully slow. Regards, Roger.
