linux-kernel - Re: [PATCHv6 01/16] x86/cpu: Enumerate the LASS feature bits

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Message-ID: <20250623102105.GCaFkqkatFSbyl1YeN@fat_crate.local>
Date: Mon, 23 Jun 2025 12:21:05 +0200
From: Borislav Petkov <bp@...en8.de>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
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	Yian Chen <yian.chen@...el.com>
Subject: Re: [PATCHv6 01/16] x86/cpu: Enumerate the LASS feature bits

On Mon, Jun 23, 2025 at 11:17:02AM +0300, Kirill A. Shutemov wrote:
> What about this:
> 
> LASS provides protection against a class of speculative attacks, such as
> SLAM[1]. Add the "lass" flag to /proc/cpuinfo to indicate that the feature
> is supported by hardware and enabled by the kernel. This allows userspace
> to determine if the setup is secure against such attacks.

Yeah, thanks.

I'm still not fully on board with userspace determining whether they're
mitigated or not but that's a general problem with our mitigations.

Also, I haven't looked at the patchset yet but I think it should be also
adding code to bugs.c to make all those vulns which it addresses, report that
they're mitigated by LASS now in

grep -r . /sys/devices/system/cpu/vulnerabilities/

output.

Which makes your cpuinfo flag not really needed as we already have a special
method for the mitigations reporting.

But ok, it has gotten kernel enablement so stating so in cpuinfo is ok.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette