linux-kernel - Re: [PATCH v3 05/10] x86/fpu/xstate: Define new functions for clearing fpregs and xstates

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Message-ID: <c0177f20d14bd607b8293a802bb16782fae5113d.camel@intel.com>
Date:   Wed, 29 Apr 2020 09:09:12 -0700
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 05/10] x86/fpu/xstate: Define new functions for
 clearing fpregs and xstates

On Wed, 2020-04-29 at 11:27 +0200, Borislav Petkov wrote:
> On Sat, Mar 28, 2020 at 09:43:02AM -0700, Yu-cheng Yu wrote:
> > @@ -318,18 +313,40 @@ static inline void copy_init_fpstate_to_fpregs(void)
> >   * Called by sys_execve(), by the signal handler code and by various
> >   * error paths.
> >   */
> > -void fpu__clear(struct fpu *fpu)
> > +static void fpu__clear(struct fpu *fpu, int clear_user_only)
> 
> I said:
> 
> "fpu__clear(struct fpu *fpu, bool user_only)"
> 			     ^^^^^^^^^^^^^^
> 
> you made it
> 
> 		     ..., int clear_user_only)
> 
> Why?
> 
> If you agree with the review comment, then please do it as suggested. If
> you don't, then say why you don't.
> 
> Why would you do something in-between?
> 
> >  {
> > -	WARN_ON_FPU(fpu != &current->thread.fpu); /* Almost certainly an anomaly */
> 
> Why are you moving this into the callers when *both* do it?
> 
> > +	if (static_cpu_has(X86_FEATURE_FPU)) {
> 
> Flip this logic:
> 
> 	if (!static_cpu_has(X86_FEATURE_FPU)) {
>                 fpu__drop(fpu);
>                 fpu__initialize(fpu);
> 		return;
> 	}
> 
> 	fpregs_lock();
> 	...
> 
> to save an indentation level and make the important case more readable
> and locking more prominent.

All fixed.

Thanks,
Yu-cheng