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Date: Mon, 21 Sep 2026 11:07:04 +0100
From: Mark Rutland <mark.rutland@arm.com>
To: David Laight <david.laight.linux@gmail.com>
Cc: Heiko Carstens <hca@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Mete Durlu <meted@linux.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juergen Christ <jchrist@linux.ibm.com>,
	Ilya Leoshkevich <iii@linux.ibm.com>, linux-kernel@vger.kernel.org,
	linux-s390@vger.kernel.org
Subject: Re: [PATCH v3 11/11] s390/percpu: Rework to simplify percpu_entry()
 and percpu_exit()
Message-ID: <arEByH7VvkEvy9Fk@J2N7QTR9R3>
References: <20260921084005.4022574-1-hca@linux.ibm.com>
 <20260921084005.4022574-12-hca@linux.ibm.com>
 <20260921105518.26f3dcf7@pumpkin>
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In-Reply-To: <20260921105518.26f3dcf7@pumpkin>

On Mon, Sep 21, 2026 at 10:55:18AM +0100, David Laight wrote:
> On Mon, 21 Sep 2026 10:40:05 +0200
> Heiko Carstens <hca@linux.ibm.com> wrote:

> > +	regpcp = FIELD_GET(PCPU_REG_PCP, regval);
> > +	regoff = FIELD_GET(PCPU_REG_OFF, regval);
> ...
> > +#define PCPU_REG_PCP_SHIFT		0
> > +#define PCPU_REG_PCP			GENMASK(3, 0)
> > +#define PCPU_REG_OFF_SHIFT		4
> > +#define PCPU_REG_OFF			GENMASK(7, 4)
> ...
> > +#define __PCPU_CALC_REGVAL(regpcp, regoff)					\
> > +	"(" regpcp " << " __stringify(PCPU_REG_PCP_SHIFT) ") |"			\
> > +	"(" regoff " << " __stringify(PCPU_REG_OFF_SHIFT) ")"
> 
> I'm not a big fan of GENMASK() + FIELD_GET() and I'm not at all sure it
> really helps here.

It's the same pattern already used by the extable code. 

While _you_ don't like it, that's not a universal opinion (and FWIW, I
prefer the FIELD_GET() approach).

I'll leave it to Heiko and co to choose whatever style they prefer, as
it's their architecture port...

Mark.