linux-kernel - Re: [PATCH] x86/nospec: Unwreck the RSB stuffing

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Message-ID: <YvyQzHzLJpalcvbZ@worktop.programming.kicks-ass.net>
Date:   Wed, 17 Aug 2022 08:55:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Daniel Sneddon <daniel.sneddon@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Borislav Petkov <bp@...e.de>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH] x86/nospec: Unwreck the RSB stuffing

On Tue, Aug 16, 2022 at 11:04:36AM -0700, Daniel Sneddon wrote:
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 1a31ae6d758b..c5b55c9f2849 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -420,7 +420,7 @@
>  #define X86_FEATURE_V_TSC_AUX          (19*32+ 9) /* "" Virtual TSC_AUX */
>  #define X86_FEATURE_SME_COHERENT       (19*32+10) /* "" AMD hardware-enforced
> cache coherency */
> 
> -#define X86_FEATURE_NEVER              (-1) /* "" Logical complement of ALWAYS */
> +#define X86_FEATURE_NEVER              (0x7FFF) /* "" Logical complement of
> ALWAYS */


Bah, I initially spelled that: ALT_NOT(X86_FEATURE_ALWAYS), but Boris
made me do the -1 thing there. Oh well, Boris can fix that :-)