Re: [PATCH v5 1/3] x86/cpu: Clear feature bits disabled at compile-time

[H. Peter Anvin]

On 2026-02-12 16:58, Borislav Petkov wrote:
> On Thu, Feb 12, 2026 at 04:14:07PM -0800, Sohil Mehta wrote:
>> So, as of today, if one of these features shows up, a user can't be sure
>> whether the kernel has enabled it or not. Right?
> 
> This is not such a critical bug - judging by how no one noticed it until
> now...
> 
>> My suggestion is that:
>> Instead of (or maybe along with) fixing this buggy interface, would it
>> be better to put this information in something like debugfs/sysfs? So,
>> at least new user software can start using that.
> 
> ... to go and make big waves and "fix" everything. We'll address this
> inconsistency eventually and go on with our lives.
> 

Agreed. And more importantly, like it or not, /proc/cpuinfo is what people are
using, if they aren't going straight out and looking at CPUID and XCR0 in user
space directly.

A new more structured interface might be nice -- for one thing, /proc/cpuinfo
is huge on newer machines; it was originally designed for the UP world -- but
we can't get rid of /proc/cpuinfo for many, many years so let's actually fix it.

	-hpa