[PATCH v10 19/40] arm64/gcs: Context switch GCS state for EL0

[Mark Brown]

On Mon, Aug 19, 2024 at 04:44:52PM +0100, Mark Brown wrote:
> On Mon, Aug 19, 2024 at 12:46:13PM +0100, Catalin Marinas wrote:
> > On Thu, Aug 01, 2024 at 01:06:46PM +0100, Mark Brown wrote:

> > > +	/*
> > > +	 * Ensure that GCS changes are observable by/from other PEs in
> > > +	 * case of migration.
> > > +	 */
> > > +	if (task_gcs_el0_enabled(current) || task_gcs_el0_enabled(next))
> > > +		gcsb_dsync();

> > Could we do the sysreg writing under this 'if' block? If no app is using
> > GCS (which would be the case for a while), it looks like unnecessary
> > sysreg accesses.

> Yes, that should be fine I think.

I forgot when writing the above that we always allow reads from
GCSPR_EL0 in order to avoid corner cases for unwinders in the case of
asynchronous disable.  I'd expect that to be cheap to access though.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 488 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-riscv/attachments/20240820/89ded92d/attachment.sig>