Date:   Tue, 14 Feb 2023 13:59:21 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Kai Huang <kai.huang@intel.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-mm@kvack.org, dave.hansen@intel.com, tglx@linutronix.de,
        seanjc@google.com, pbonzini@redhat.com, dan.j.williams@intel.com,
        rafael.j.wysocki@intel.com, kirill.shutemov@linux.intel.com,
        ying.huang@intel.com, reinette.chatre@intel.com,
        len.brown@intel.com, tony.luck@intel.com, ak@linux.intel.com,
        isaku.yamahata@intel.com, chao.gao@intel.com,
        sathyanarayanan.kuppuswamy@linux.intel.com, david@redhat.com,
        bagasdotme@gmail.com, sagis@google.com, imammedo@redhat.com
Subject: Re: [PATCH v9 07/18] x86/virt/tdx: Do TDX module per-cpu
 initialization
Message-ID: <Y+uFqYRZELDquAJ7@hirez.programming.kicks-ass.net>
References: <cover.1676286526.git.kai.huang@intel.com>
 <557c526a1190903d11d67c4e2c76e01f67f6eb15.1676286526.git.kai.huang@intel.com>
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On Tue, Feb 14, 2023 at 12:59:14AM +1300, Kai Huang wrote:
> +/*
> + * Call @func on all online cpus one by one but skip those cpus
> + * when @skip_func is valid and returns true for them.
> + */
> +static int tdx_on_each_cpu_cond(int (*func)(void *), void *func_data,
> +				bool (*skip_func)(int cpu, void *),
> +				void *skip_data)
> +{
> +	int cpu;
> +
> +	for_each_online_cpu(cpu) {
> +		int ret;
> +
> +		if (skip_func && skip_func(cpu, skip_data))
> +			continue;
> +
> +		/*
> +		 * SEAMCALL can be time consuming.  Call the @func on
> +		 * remote cpu via smp_call_on_cpu() instead of
> +		 * smp_call_function_single() to avoid busy waiting.
> +		 */
> +		ret = smp_call_on_cpu(cpu, func, func_data, true);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}

schedule_on_each_cpu() ?