Re: [PATCH v12 02/29] arm64/fpsimd: Update FA64 and ZT0 enables when loading SME state

[Mark Brown]

On Thu, Jul 16, 2026 at 11:52:36AM +0100, Mark Rutland wrote:

> >  		if (test_thread_flag(TIF_SME)) {
> > -			unsigned long vq = sve_vq_from_vl(sme_vl);
> > -			sysreg_clear_set_s(SYS_SMCR_EL1, SMCR_ELx_LEN, vq - 1);
> > +			sysreg_cond_update_s(SYS_SMCR_EL1, task_smcr(current));
> > +			isb();
> >  		}

> What's the ISB for? That mysteriously appeared in v11 without
> explanation. It wasn't in the original code, prior versions of the
> series, or my suggested rework with the task_smcr() helper.

> I don't believe it's necessary to add an ISB here.

I can't remember or figure it out, I'll delete.

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