Re: [PATCH v4 4/4] arm64: escalate smp_send_stop() to an SDEI NMI as a last resort
Catalin Marinas <[email protected]>
| Newsgroups | org.infradead.lists.kexec,org.infradead.lists.linux-arm-kernel,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
On Wed, Jun 17, 2026 at 08:20:05PM +0100, Kiryl Shutsemau wrote:
> +void sdei_nmi_stop_cpus(const cpumask_t *mask)
> +{
> + unsigned int cpu;
> +
> + WRITE_ONCE(sdei_nmi_stopping, true);
> +
> + /*
> + * Publish the flag before signalling. The SMC is a context-sync
> + * event, not a barrier, so WRITE_ONCE() alone could let the store be
> + * observed after the event it triggers. The barrier is cumulative: a
> + * target that sees the event is guaranteed to see the flag.
> + */
> + smp_wmb();
> +
> + for_each_cpu(cpu, mask)
> + sdei_nmi_fire(cpu);
> +}
The smp_wmb() is not sufficient here. In the GIC IPI code we use a
dsb(ishst). It should be similar here. I think TF-A does this already
but it's unclear from the SDEI spec that it is mandated.
--
Catalin