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

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Message-ID: <20251023160536.sq57f5rtwlgrryqr@desk>
Date: Thu, 23 Oct 2025 09:05:36 -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>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"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 Thu, Oct 23, 2025 at 08:45:10AM +0200, Petr Tesarik wrote:
> 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.

I would let the maintainers decide how they want it.

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

Borislav, Dave?