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

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Message-ID: <20251023084510.4b1cd2fe@mordecai>
Date: Thu, 23 Oct 2025 08:45:10 +0200
From: Petr Tesarik <ptesarik@...e.com>
To: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Thomas Gleixner
 <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
 <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.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, 22 Oct 2025 10:46:03 -0700
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com> wrote:

> 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.

Matter of taste if you ask me. I have no preference either way, so if
you do have an opinion, let's write it your way.

Do I have to resubmit, or can an x86 maintainer adjust it when applying
the patch?

Petr T