Re: [PATCH v4 3/7] x86/sev: Initialize RMPOPT configuration MSRs

[Ackerley Tng]

Ashish Kalra <Ashish.Kalra@xxxxxxx> writes:

>
> [...snip...]
>
> +void snp_setup_rmpopt(void)
> +{
> +	u64 rmpopt_base;
> +	int cpu;
> +
> +	if (!cpu_feature_enabled(X86_FEATURE_RMPOPT))
> +		return;
> +
> +	/*
> +	 * RMPOPT_BASE MSR is per-core, so only one thread per core needs to
> +	 * setup RMPOPT_BASE MSR.
> +	 */
> +
> +	for_each_online_cpu(cpu) {

Dave mentioned hotplug in v3 [1], which led me to check. From this
series, it looks like RMPOPT won't ever be performed for newly-plugged
cpus, is that okay?

> +		if (!topology_is_primary_thread(cpu))
> +			continue;
> +
> +		cpumask_set_cpu(cpu, &rmpopt_cpumask);

nit: perhaps flipping the condition is easier to read:

    if (topology_is_primary_thread(cpu))
    	cpumask_set_cpu()

> +	}
> +
> +	rmpopt_pa_start = ALIGN_DOWN(PFN_PHYS(min_low_pfn), SZ_1G);
> +	rmpopt_base = rmpopt_pa_start | MSR_AMD64_RMPOPT_ENABLE;
> +
> +	/*
> +	 * Per-CPU RMPOPT tables support at most 2 TB of addressable memory
> +	 * for RMP optimizations. Initialize the per-CPU RMPOPT table base
> +	 * to the starting physical address to enable RMP optimizations for
> +	 * up to 2 TB of system RAM on all CPUs.
> +	 */
> +	wrmsrq_on_cpus(&rmpopt_cpumask, MSR_AMD64_RMPOPT_BASE, rmpopt_base);
> +}

[1] https://lore.kernel.org/all/ab41b1d8-e464-4ad6-ac07-7318686db10e@xxxxxxxxx/

>
> [...snip...]
>