Re: [PATCH v6 01/25] x86/fpu/xstate: Manually check and add XFEATURE_CET_USER xstate bit

[Yang, Weijiang]

On 9/16/2023 12:35 AM, Edgecombe, Rick P wrote:
> On Fri, 2023-09-15 at 10:32 +0800, Yang, Weijiang wrote:
> > > Also, this doesn't discuss the real main reason for this patch, and
> > > that is that KVM will soon use the xfeature for user ibt, and so
> > > there
> > > will now be a reason to have XFEATURE_CET_USER depend on IBT.
> > This is one justification for Linux OS, another reason is there's
> > non-Linux
> > OS which is using the user IBT feature.  I should make the reasons
> > clearer
> > in changelog, thanks for pointing it out!
> The point I was trying to make was today (before this series) nothing
> on the system can use user IBT. Not the host, and not in any guest
> because KVM doesn't support it. So the added xfeature dependency on IBT
> was not previously needed. It is being added only for KVM CET support
> (which, yes, may run on guests with non-standard CPUID).

Agree, I'll highlight this in changelog, thanks!