linux-kernel - Re: [PATCH v4 next 4/9] lib: Add mul_u64_add_u64_div_u64() and mul_u64_u64_div_u64

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Message-Id: <20251031191241.c3d0fa93219cab2a1157fe1e@linux-foundation.org>
Date: Fri, 31 Oct 2025 19:12:41 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: David Laight <david.laight.linux@...il.com>
Cc: linux-kernel@...r.kernel.org, u.kleine-koenig@...libre.com, Nicolas
 Pitre <npitre@...libre.com>, Oleg Nesterov <oleg@...hat.com>, Peter
 Zijlstra <peterz@...radead.org>, Biju Das <biju.das.jz@...renesas.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Thomas
 Gleixner <tglx@...utronix.de>, Li RongQing <lirongqing@...du.com>, Yu Kuai
 <yukuai3@...wei.com>, Khazhismel Kumykov <khazhy@...omium.org>, Jens Axboe
 <axboe@...nel.dk>, x86@...nel.org
Subject: Re: [PATCH v4 next 4/9] lib: Add mul_u64_add_u64_div_u64() and
 mul_u64_u64_div_u64_roundup()

On Fri, 31 Oct 2025 20:59:17 +0000 David Laight <david.laight.linux@...il.com> wrote:

> > -static inline u64 mul_u64_u64_div_u64(u64 a, u64 mul, u64 div)
> > +static inline u64 mul_u64_add_u64_div_u64(u64 rax, u64 mul, u64 add, u64 div)
> >  {
> > -	u64 q;
> > +	u64 rdx;
> >  
> > -	asm ("mulq %2; divq %3" : "=a" (q)
> > -				: "a" (a), "rm" (mul), "rm" (div)
> > -				: "rdx");
> > +	asm ("mulq %[mul]" : "+a" (rax), "=d" (rdx) : [mul] "rm" (mul));
> >  
> > -	return q;
> > +	if (statically_true(add))
> 
> This needs to be:
> 	if (!statically_true(!add))
> 
> Do you need me to resend the full series?

I queued a fix, thanks.

--- a/arch/x86/include/asm/div64.h~lib-add-mul_u64_add_u64_div_u64-and-mul_u64_u64_div_u64_roundup-fix
+++ a/arch/x86/include/asm/div64.h
@@ -90,7 +90,7 @@ static inline u64 mul_u64_add_u64_div_u6

 	asm ("mulq %[mul]" : "+a" (rax), "=d" (rdx) : [mul] "rm" (mul));

-	if (statically_true(add))
+	if (!statically_true(add))
 		asm ("addq %[add], %[lo]; adcq $0, %[hi]" :
 			[lo] "+r" (rax), [hi] "+r" (rdx) : [add] "irm" (add));

_