linux-kernel - Re: [PATCH net-next V6] net/mlx5: Improve write-combining test reliability for ARM64 Grace CPUs

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Message-ID: <e77083c4-82ac-0c95-1cf1-5a13f15e7c58@redhat.com>
Date: Mon, 6 Oct 2025 15:57:38 +0200 (CEST)
From: Sebastian Ott <sebott@...hat.com>
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>, 
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    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>, 
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    Ingo Molnar <mingo@...hat.com>, Bill Wendling <morbo@...gle.com>, 
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    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>, Simon Horman <horms@...nel.org>, 
    Patrisious Haddad <phaddad@...dia.com>
Subject: Re: [PATCH net-next V6] net/mlx5: Improve write-combining test
 reliability for ARM64 Grace CPUs

On Mon, 29 Sep 2025, 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 IS_ENABLED(CONFIG_KERNEL_MODE_NEON) && IS_ENABLED(CONFIG_ARM64)
> +	if (cpu_has_neon()) {
> +		kernel_neon_begin();
> +		asm volatile
> +		(".arch_extension simd;\n\t"
> +		"ld1 {v0.16b, v1.16b, v2.16b, v3.16b}, [%0]\n\t"
> +		"st1 {v0.16b, v1.16b, v2.16b, v3.16b}, [%1]"
> +		:
> +		: "r"(mmio_wqe), "r"(sq->bfreg.map + offset)
> +		: "memory", "v0", "v1", "v2", "v3");
> +		kernel_neon_end();
> +		return;
> +	}
> +#endif

This one breaks the build for me:
/tmp/cc2vw3CJ.s: Assembler messages:
/tmp/cc2vw3CJ.s:391: Error: unknown architectural extension `simd;'

Removing the extra ";" after simd seems to fix it.

Regards,
Sebastian