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Date:   Fri, 11 Jun 2021 12:03:41 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Jonathan Corbet <corbet@lwn.net>,
        Peter Zijlstra <peterz@infradead.org>,
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        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
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Subject: Re: [PATCH 3/4] x86/tsx: Clear CPUID bits when TSX always force
 aborts
Message-ID: <YMM0/SARv62uo41r@zn.tnic>
References: <cover.2d906c322f72ec1420955136ebaa7a4c5073917c.1623272033.git-series.pawan.kumar.gupta@linux.intel.com>
 <aaf129dab23878913bf6f370894c336fc45388a2.1623272033.git-series.pawan.kumar.gupta@linux.intel.com>
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On Wed, Jun 09, 2021 at 02:13:38PM -0700, Pawan Gupta wrote:
> @@ -114,6 +127,26 @@ void __init tsx_init(void)
>  			tsx_ctrl_state = TSX_CTRL_ENABLE;
>  	}
>  
> +	/*
> +	 * Hardware will always abort a TSX transaction if both CPUID bits
> +	 * RTM_ALWAYS_ABORT and TSX_FORCE_ABORT are enumerated.  In this case it
> +	 * is better not to enumerate CPUID.RTM and CPUID.HLE bits. Clear them
> +	 * here.
> +	 */
> +	if (boot_cpu_has(X86_FEATURE_RTM_ALWAYS_ABORT) &&
> +	    boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT)) {
> +		tsx_ctrl_state = TSX_CTRL_RTM_ALWAYS_ABORT;
> +		tsx_clear_cpuid();
> +		setup_clear_cpu_cap(X86_FEATURE_RTM);
> +		setup_clear_cpu_cap(X86_FEATURE_HLE);
> +		return;
> +	}

Why isn't this happening as the first thing on entry in that tsx_init()
function? IOW, there's no point to noodle through cmdline options etc if
the hardware will always abort transactions.

-- 
Regards/Gruss,
    Boris.

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