linux-kernel - Re: [PATCH v11 21/39] arm64/gcs: Ensure that new threads have a GCS

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Message-ID: <ZsdmRHinYQdbPn9p@finisterre.sirena.org.uk>
Date: Thu, 22 Aug 2024 17:24:36 +0100
From: Mark Brown <broonie@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
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	Shuah Khan <shuah@...nel.org>,
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Subject: Re: [PATCH v11 21/39] arm64/gcs: Ensure that new threads have a GCS

On Thu, Aug 22, 2024 at 05:17:14PM +0100, Catalin Marinas wrote:

> >  	/*
> > -	 * Ensure that GCS changes are observable by/from other PEs in
> > -	 * case of migration.
> > +	 * Ensure that GCS memory effects of the 'prev' thread are
> > +	 * ordered before other memory accesses with release semantics
> > +	 * (or preceded by a DMB) on the current PE. In addition, any
> > +	 * memory accesses with acquire semantics (or succeeded by a
> > +	 * DMB) are ordered before GCS memory effects of the 'next'
> > +	 * thread. This will ensure that the GCS memory effects are
> > +	 * visible to other PEs in case of migration.
> >  	 */
> > -	gcsb_dsync();
> > +	if (task_gcs_el0_enabled(current) || task_gcs_el0_enabled(next))
> > +		gcsb_dsync();

> Ah, the comment turned up in this patch. It looks fine.

Oh, sorry - I should probably just pull this hunk into the other patch.

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