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 S1751218AbdEaS31 (ORCPT <rfc822;w@1wt.eu>);
        Wed, 31 May 2017 14:29:27 -0400
Received: from foss.arm.com ([217.140.101.70]:47900 "EHLO foss.arm.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751004AbdEaS30 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 31 May 2017 14:29:26 -0400
Subject: Re: [PATCH] irqchip/gic-v3-its: Fix MSI alias accounting
To: Robin Murphy <robin.murphy@arm.com>, tglx@linutronix.de,
        jason@lakedaemon.net
References: <20170531175230.16529-1-robin.murphy@arm.com>
Cc: linux-kernel@vger.kernel.org
From: Marc Zyngier <marc.zyngier@arm.com>
Organization: ARM Ltd
Message-ID: <ce88232d-654c-cdc0-89dc-f81ff769fdba@arm.com>
Date: Wed, 31 May 2017 19:29:23 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Thunderbird/45.8.0
MIME-Version: 1.0
In-Reply-To: <20170531175230.16529-1-robin.murphy@arm.com>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 31/05/17 18:52, Robin Murphy wrote:
> The call to pci_for_each_dma_alias() in the ITS PCI code has aroused
> suspicion in the past, and upon closer inspection does turn out to be
> completely backwards. Rather than iterating through each RID alias of
> the given device, what we actually want to be doing here is iterating
> through all the *other* devices which may also alias the same RID, in
> order to size the table for the worst case.
> 
> Do the right thing by ignoring the initial DMA aliases themselves and
> just using that walk to detect an aliasing bridge, then walking back
> down the bus topology as necessary to actually count everything else.
> 
> Our alias handling still isn't perfect, since we don't account for the
> cases of certain bridges only taking ownership of transactions under
> particular circumstances, but without completely reworking the ITS code
> to cope with the notion of multiple DevIDs per device, it'll have to do.
> 
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Ah, that's pretty neat.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

I'll queue this for 4.13.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...