linux-kernel - Re: [PATCH v6 05/07] iommu/ipmmu-vmsa: Add new IOMMU_DOMAIN

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Message-ID: <20161110114206.GC9996@8bytes.org>
Date:   Thu, 10 Nov 2016 12:42:06 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Magnus Damm <magnus.damm@...il.com>,
        iommu@...ts.linux-foundation.org,
        laurent.pinchart+renesas@...asonboard.com, geert+renesas@...der.be,
        linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        horms+renesas@...ge.net.au, m.szyprowski@...sung.com
Subject: Re: [PATCH v6 05/07] iommu/ipmmu-vmsa: Add new IOMMU_DOMAIN_DMA ops

On Fri, Oct 21, 2016 at 06:52:53PM +0100, Robin Murphy wrote:
> > -static struct iommu_domain *ipmmu_domain_alloc(unsigned type)
> > -{
> > -	if (type != IOMMU_DOMAIN_UNMANAGED)
> > -		return NULL;
> 
> I *think* that if we did the initial check thus:
> 
> 	if (type != IOMMU_DOMAIN_UNMANAGED ||
> 	    (IS_ENABLED(CONFIG_IOMMU_DMA) && type != IOMMU_DOMAIN_DMA))
> 		return NULL;
> 
> it shouldn't be necessary to split the function at all - we then just
> wrap the {get,put}_cookie() bits in "if (type ==  IOMMU_DOMAIN_DMA)" and
> in the 32-bit ARM case they just don't run as that can never be true.

This would be a good improvement. Magnus, Robin, can either of you send
a follow-on patch to implement this suggestion? I have applied these
patches to my arm/renesas branch (not pushed yet). The patch can be
based on it.


	Joerg