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

Catalin Marinas
2024-08-22T16:17:22Z

On Thu, Aug 22, 2024 at 02:15:24AM +0100, Mark Brown wrote:
> @@ -512,10 +538,16 @@ static void gcs_thread_switch(struct task_struct *next)
> gcs_set_el0_mode(next);
>
> /*
> - * 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.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>