Re: [PATCH 3/8] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest

[Konrad Rzeszutek Wilk]

On Wed, Jan 10, 2018 at 03:28:43PM +0100, Paolo Bonzini wrote:
> On 10/01/2018 15:06, Arjan van de Ven wrote:
> > On 1/10/2018 5:20 AM, Paolo Bonzini wrote:
> >> * a simple specification that does "IBRS=1 blocks indirect branch
> >> prediction altogether" would actually satisfy the specification just as
> >> well, and it would be nice to know if that's what the processor actually
> >> does.
> > 
> > it doesn't exactly, not for all.
> > 
> > so you really do need to write ibrs again.
> 
> Okay, so "always set IBRS=1" does *not* protect against variant 2.  Thanks,

And what is the point of this "always set IBRS=1" then? Are there some other
things lurking in the shadows?
> 
> Paolo