linux-kernel - Re: [PATCH v3 2/2] x86/tsx: Get the tsx= command line parameter with early

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Message-ID: <20251022174603.mx7sze3w5e24obps@desk>
Date: Wed, 22 Oct 2025 10:46:03 -0700
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: Petr Tesarik <ptesarik@...e.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Nikolay Borisov <nik.borisov@...e.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
	"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] x86/tsx: Get the tsx= command line parameter with
 early_param()

On Wed, Oct 22, 2025 at 12:26:13PM +0200, Petr Tesarik wrote:
> Use early_param() to get the value of the tsx= command line parameter. It
> is an early parameter, because it must be parsed before tsx_init(), which
> is called long before kernel_init(), where normal parameters are parsed.
> 
> Although cmdline_find_option() from tsx_init() works fine, the option is
> later reported as unknown and passed to user space. The latter is not a
> real issue, but the former is confusing and makes people wonder if the tsx=
> parameter had any effect and double-check for typos unnecessarily.
> 
> The behavior changes slightly if "tsx" is given without any argument (which
> is invalid syntax). Prior to this patch, the kernel logged an error message
> and disabled TSX. With this patch, the kernel still issues a warning
> (Malformed early option 'tsx'), but TSX state is unchanged. The new
> behavior is consistent with other parameters, e.g. "tsx_async_abort".
> 
> Suggested-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
> Signed-off-by: Petr Tesarik <ptesarik@...e.com>
> ---
>  arch/x86/kernel/cpu/tsx.c | 52 ++++++++++++++++++++-------------------
>  1 file changed, 27 insertions(+), 25 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/tsx.c b/arch/x86/kernel/cpu/tsx.c
> index 8be08ece2214..74ba4abac7e9 100644
> --- a/arch/x86/kernel/cpu/tsx.c
> +++ b/arch/x86/kernel/cpu/tsx.c
> @@ -20,13 +20,17 @@
>  #define pr_fmt(fmt) "tsx: " fmt
>  
>  enum tsx_ctrl_states {
> +	TSX_CTRL_AUTO,
>  	TSX_CTRL_ENABLE,
>  	TSX_CTRL_DISABLE,
>  	TSX_CTRL_RTM_ALWAYS_ABORT,
>  	TSX_CTRL_NOT_SUPPORTED,
>  };
>  
> -static enum tsx_ctrl_states tsx_ctrl_state __ro_after_init = TSX_CTRL_NOT_SUPPORTED;
> +static enum tsx_ctrl_states tsx_ctrl_state __ro_after_init =
> +	IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_AUTO) ? TSX_CTRL_AUTO :
> +	IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_OFF) ? TSX_CTRL_DISABLE :
                                                 ^
						 The extra space I had in
						 the version I sent was
						 intentional.

> +	TSX_CTRL_ENABLE;

Also this can stay on the same line.

	IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_AUTO) ? TSX_CTRL_AUTO    :
	IS_ENABLED(CONFIG_X86_INTEL_TSX_MODE_OFF)  ? TSX_CTRL_DISABLE : TSX_CTRL_ENABLE;

IMO, this is so much more easier to read.