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

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Message-ID: <tfpekzid4hu4xguq3fetosyltg3owjy2cactqklohfohalhbza@hx7qdrpcymrn>
Date: Fri, 20 Jun 2025 20:31:14 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Xin Li <xin@...or.com>
Cc: Andy Lutomirski <luto@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
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	"Paul E. McKenney" <paulmck@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>, 
	Xiongwei Song <xiongwei.song@...driver.com>, Xin Li <xin3.li@...el.com>, 
	"Mike Rapoport (IBM)" <rppt@...nel.org>, Brijesh Singh <brijesh.singh@....com>, 
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	linux-mm@...ck.org, Yian Chen <yian.chen@...el.com>
Subject: Re: [PATCHv6 01/16] x86/cpu: Enumerate the LASS feature bits

On Fri, Jun 20, 2025 at 08:36:30AM -0700, Xin Li wrote:
> On 6/20/2025 6:53 AM, Kirill A. Shutemov wrote:
> > diff --git a/arch/x86/Kconfig.cpufeatures b/arch/x86/Kconfig.cpufeatures
> > index 250c10627ab3..9574c198fc08 100644
> > --- a/arch/x86/Kconfig.cpufeatures
> > +++ b/arch/x86/Kconfig.cpufeatures
> > @@ -124,6 +124,10 @@ config X86_DISABLED_FEATURE_PCID
> >   	def_bool y
> >   	depends on !X86_64
> > +config X86_DISABLED_FEATURE_LASS
> > +	def_bool y
> > +	depends on !X86_64
> > +
> >   config X86_DISABLED_FEATURE_PKU
> >   	def_bool y
> >   	depends on !X86_INTEL_MEMORY_PROTECTION_KEYS
> 
> You don't need to add X86_DISABLED_FEATURE_LASS, because the LASS code
> is NOT optional at build time, i.e., you now don't have CONFIG_X86_LASS.

Hmm. But it is optional. It depends on CONFIG_X86_64. I don't think we
want it to be advertised on 32-bit kernels.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov