netdev - Re: [PATCH net-next V3] net/mlx5: Improve write-combining test reliability for ARM64 Grace CPUs

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Message-ID: <20250918150727.GX394836@horms.kernel.org>
Date: Thu, 18 Sep 2025 16:07:27 +0100
From: Simon Horman <horms@...nel.org>
To: Tariq Toukan <tariqt@...dia.com>
Cc: 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>,
	Jason Gunthorpe <jgg@...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>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Justin Stitt <justinstitt@...gle.com>, linux-s390@...r.kernel.org,
	llvm@...ts.linux.dev, Ingo Molnar <mingo@...hat.com>,
	Bill Wendling <morbo@...gle.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Salil Mehta <salil.mehta@...wei.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	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>,
	Patrisious Haddad <phaddad@...dia.com>
Subject: Re: [PATCH net-next V3] net/mlx5: Improve write-combining test
 reliability for ARM64 Grace CPUs

On Thu, Sep 18, 2025 at 10:01:23AM +0300, Tariq Toukan wrote:
> From: Patrisious Haddad <phaddad@...dia.com>
> 
> Write combining is an optimization feature in CPUs that is frequently
> used by modern devices to generate 32 or 64 byte TLPs at the PCIe level.
> These large TLPs allow certain optimizations in the driver to HW
> communication that improve performance. As WC is unpredictable and
> optional the HW designs all tolerate cases where combining doesn't
> happen and simply experience a performance degradation.

...

> Signed-off-by: Patrisious Haddad <phaddad@...dia.com>
> Reviewed-by: Michael Guralnik <michaelgur@...dia.com>
> Reviewed-by: Moshe Shemesh <moshe@...dia.com>
> Signed-off-by: Tariq Toukan <tariqt@...dia.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/wc.c | 28 ++++++++++++++++++--
>  1 file changed, 26 insertions(+), 2 deletions(-)
> 
> Find V2 here:
> https://lore.kernel.org/all/1757925308-614943-1-git-send-email-tariqt@nvidia.com/
> 
> V3:
> - Move the new copy assembly code to be inline, within the same file it
>   is used.
> - Use ".arch_extension simd;\n\t" to avoid the need for separate file
>   and special compilation flags.

Hi Tariq, Patrisious, all,

This is not a full review - although I've been following this patch with
much interest, I don't feel qualified to provide one.

But what I can do is be the poor soul to report that unfortunately
the patch doesn't compile against net-next. So at some point it will
need to be rebased and reposted.

Thanks for your persistence on working on this, it is indeed a nettlesome issue.

-- 
pw-bot: changes-requested