From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1755476AbdJLJWg (ORCPT <rfc822;w@1wt.eu>);
        Thu, 12 Oct 2017 05:22:36 -0400
Received: from Galois.linutronix.de ([146.0.238.70]:36290 "EHLO
        Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751420AbdJLJWf (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 12 Oct 2017 05:22:35 -0400
Date: Thu, 12 Oct 2017 11:22:20 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Marc Zyngier <marc.zyngier@arm.com>
cc: linux-kernel@vger.kernel.org, Jason Cooper <jason@lakedaemon.net>,
        Shanker Donthineni <shankerd@codeaurora.org>,
        Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
        Christoffer Dall <cdall@linaro.org>,
        Eric Auger <eric.auger@redhat.com>
Subject: Re: [PATCH 10/10] irqchip/gic-v4: Make the doorbells managed affinity
 interrupts
In-Reply-To: <20171010125137.9464-11-marc.zyngier@arm.com>
Message-ID: <alpine.DEB.2.20.1710121118200.1930@nanos>
References: <20171010125137.9464-1-marc.zyngier@arm.com> <20171010125137.9464-11-marc.zyngier@arm.com>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
X-Linutronix-Spam-Score: -1.0
X-Linutronix-Spam-Level: -
X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required,  ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, 10 Oct 2017, Marc Zyngier wrote:
>  int its_alloc_vcpu_irqs(struct its_vm *vm)
>  {
>  	int vpe_base_irq, i;
>  
> +	vm->affinity_masks = kzalloc(vm->nr_vpes * sizeof(*vm->affinity_masks),
> +				     GFP_KERNEL);
> +	if (!vm->affinity_masks)
> +		goto err;
> +
> +	for (i = 0; i < vm->nr_vpes; i++) {
> +		if (!alloc_cpumask_var(&vm->affinity_masks[i], GFP_KERNEL))
> +			goto err;
> +
> +		cpumask_copy(vm->affinity_masks[i], cpu_possible_mask);

That looks a bit like abuse of managed interrupts as you don't use any of
the managing parts, i.e. the managed shutdown/startup on cpu hotplug.

You can prevent user space from fiddling with the affinities by flagging
these interrupts with IRQ_NO_BALANCING.

Thanks,

	tglx