linux-kernel - Re: [PATCH net-next V5] net/mlx5: Improve write-combining test reliability for ARM64 Grace CPUs

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Message-ID: <20250925122139.GW2617119@nvidia.com>
Date: Thu, 25 Sep 2025 09:21:39 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Patrisious Haddad <phaddad@...dia.com>
Cc: Tariq Toukan <tariqt@...dia.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Saeed Mahameed <saeedm@...dia.com>,
	Leon Romanovsky <leon@...nel.org>, Mark Bloch <mbloch@...dia.com>,
	netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org, Gal Pressman <gal@...dia.com>,
	Leon Romanovsky <leonro@...dia.com>,
	Michael Guralnik <michaelgur@...dia.com>,
	Moshe Shemesh <moshe@...dia.com>, Will Deacon <will@...nel.org>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Borislav Petkov <bp@...en8.de>,
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	Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
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	Heiko Carstens <hca@...ux.ibm.com>,
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	Justin Stitt <justinstitt@...gle.com>, linux-s390@...r.kernel.org,
	llvm@...ts.linux.dev, Ingo Molnar <mingo@...hat.com>,
	Bill Wendling <morbo@...gle.com>,
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	Nick Desaulniers <ndesaulniers@...gle.com>,
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	Yisen Zhuang <yisen.zhuang@...wei.com>,
	Arnd Bergmann <arnd@...db.de>,
	Leon Romanovsky <leonro@...lanox.com>, linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Mark Rutland <mark.rutland@....com>,
	Michael Guralnik <michaelgur@...lanox.com>, patches@...ts.linux.dev,
	Niklas Schnelle <schnelle@...ux.ibm.com>,
	Jijie Shao <shaojijie@...wei.com>, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net-next V5] net/mlx5: Improve write-combining test
 reliability for ARM64 Grace CPUs

On Thu, Sep 25, 2025 at 03:15:46PM +0300, Patrisious Haddad wrote:
> 
> On 9/25/2025 2:54 PM, Jason Gunthorpe wrote:
> > On Thu, Sep 25, 2025 at 02:48:33PM +0300, Tariq Toukan wrote:
> > > +static void mlx5_iowrite64_copy(struct mlx5_wc_sq *sq, __be32 mmio_wqe[16],
> > > +				size_t mmio_wqe_size, unsigned int offset)
> > > +{
> > > +#if defined(CONFIG_KERNEL_MODE_NEON) && defined(CONFIG_ARM64)
> > IS_ENABLED() not defined()
> I just wonder why, Is there a preference in the driver from like
> aesthetic/convention point of view?
> Since here it technically doesnt matter - IS_ENABLED have no functional
> difference from defined since these are boolean configs not *tristate*ones
> (cant be loaded as module).

I think it is an aesthetic convention to avoid defined(CONFIG_*) as
the reasoning it is not tristate is a bit tricky.

Jason