linux-kernel - Re: "Paravisor" Feature Enumeration

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Message-ID: <695c806beb4d7_4b7a10080@dwillia2-mobl4.notmuch>
Date: Mon, 5 Jan 2026 19:24:27 -0800
From: <dan.j.williams@...el.com>
To: Dave Hansen <dave.hansen@...el.com>, <dan.j.williams@...el.com>, "Lange,
 Jon" <jlange@...rosoft.com>
CC: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
	<pbonzini@...hat.com>, <john.starks@...rosoft.com>, Will Deacon
	<will@...nel.org>, Mark Rutland <mark.rutland@....com>,
	"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>, LKML
	<linux-kernel@...r.kernel.org>, "Kirill A. Shutemov"
	<kirill.shutemov@...ux.intel.com>, "Edgecombe, Rick P"
	<rick.p.edgecombe@...el.com>, Andrew Cooper <andrew.cooper3@...rix.com>
Subject: Re: "Paravisor" Feature Enumeration

Dave Hansen wrote:
> On 1/5/26 16:01, dan.j.williams@...el.com wrote:
> > Dave Hansen wrote:
> ...
> >> 	X86_FEATURE_KVM_CLOCKSOURCE in arm,pvclock
> >> or
> >> 	X86_FEATURE_KVM_STEAL_TIME  in arm,kvm-steal-time
> >>
> >> As far as I can tell, these aliases are all done ad-hoc. This approach
> >> could obviously be extended to paravisor features, but it would probably
> >> be on the slow side to do it for each new feature.
> > 
> > "Slow" as in standardization time?
> 
> Yes.

That speed problem is mitigated by the EFI/ACPI Code First process.
Linux and any other impacted implementation that want to be party to a
new mechanism just come to a public agreement on the mailing lists per
usual and ACPI Working Group acks/naks that public proposal. That
effectively gets you in the same ballpark of time as landing a new
invented Linux enumeration upstream.

There is a lag between the ack and the spec release, but the intention
is the ack means it is safe to assume a future version of the
specification will adopt the change.