Re: [PATCH 0/4] Add support for XMM fast hypercalls

[Paolo Bonzini]

On 08/04/21 17:40, Siddharth Chandrasekaran wrote:
> > > > Although the Hyper-v TLFS mentions that a guest cannot use this feature
> > > > unless the hypervisor advertises support for it, some hypercalls which
> > > > we plan on upstreaming in future uses them anyway.
> > > No, please don't do this. Check the feature bit(s) before you issue
> > > hypercalls which rely on the extended interface.
> > Perhaps Siddharth should clarify this, but I read it as Hyper-V being
> > buggy and using XMM arguments unconditionally.
> The guest is at fault here as it expects Hyper-V to consume arguments
> from XMM registers for certain hypercalls (that we are working) even if
> we didn't expose the feature via CPUID bits.

What guest is that?

Paolo