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Date: Tue, 4 Dec 2018 10:31:16 +0100
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC v2 13/13] keys/mktme: Support CPU Hotplug for MKTME keys
Message-ID: <20181204093116.GV11614@hirez.programming.kicks-ass.net>
References: <cover.1543903910.git.alison.schofield@intel.com>
 <c14d24b09ee2ae37ea4106726ce8fe2aea31f6c7.1543903910.git.alison.schofield@intel.com>
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To: Alison Schofield <alison.schofield@intel.com>
Cc: dhowells@redhat.com, tglx@linutronix.de, jmorris@namei.org, mingo@redhat.com, hpa@zytor.com, bp@alien8.de, luto@kernel.org, kirill.shutemov@linux.intel.com, dave.hansen@intel.com, kai.huang@intel.com, jun.nakajima@intel.com, dan.j.williams@intel.com, jarkko.sakkinen@intel.com, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org

On Mon, Dec 03, 2018 at 11:40:00PM -0800, Alison Schofield wrote:
>  static int mktme_program_system(struct mktme_key_program *key_program,
> -				cpumask_var_t mktme_cpumask)
> +				cpumask_var_t mktme_cpumask, int hotplug)
>  {
>  	struct mktme_hw_program_info info = {
>  		.key_program = key_program,
>  		.status = MKTME_PROG_SUCCESS,
>  	};
> -	get_online_cpus();
> -	on_each_cpu_mask(mktme_cpumask, mktme_program_package, &info, 1);
> -	put_online_cpus();
> +
> +	if (!hotplug) {
> +		get_online_cpus();
> +		on_each_cpu_mask(mktme_cpumask, mktme_program_package,
> +				 &info, 1);
> +		put_online_cpus();
> +	} else {
> +		on_each_cpu_mask(mktme_cpumask, mktme_program_package,
> +				 &info, 1);
> +	}
>  
>  	return info.status;
>  }

That is pretty horrible; and I think easily avoided.