linux-kernel - Re: [PATCH v5 05/07] iommu/ipmmu-vmsa: Add new IOMMU_DOMAIN

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Message-ID: <20160922144506.GK3541@8bytes.org>
Date:   Thu, 22 Sep 2016 16:45:06 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Magnus Damm <magnus.damm@...il.com>
Cc:     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, robin.murphy@....com,
        m.szyprowski@...sung.com
Subject: Re: [PATCH v5 05/07] iommu/ipmmu-vmsa: Add new IOMMU_DOMAIN_DMA ops

On Tue, Sep 20, 2016 at 10:44:46PM +0900, Magnus Damm wrote:
> +#ifdef CONFIG_IOMMU_DMA
> +
> +static struct iommu_domain *ipmmu_domain_alloc_dma(unsigned type)
> +{
> +	struct iommu_domain *io_domain;
> +
> +	if (type != IOMMU_DOMAIN_DMA)
> +		return NULL;
> +
> +	io_domain = __ipmmu_domain_alloc(type);
> +	if (io_domain)
> +		iommu_get_dma_cookie(io_domain);
> +
> +	return io_domain;
> +}
> +
> +static void ipmmu_domain_free_dma(struct iommu_domain *io_domain)
> +{
> +	iommu_put_dma_cookie(io_domain);
> +	ipmmu_domain_free(io_domain);
> +}

> [...]

> +static const struct iommu_ops ipmmu_ops = {
> +	.domain_alloc = ipmmu_domain_alloc_dma,
> +	.domain_free = ipmmu_domain_free_dma,

Okay, so when CONFIG_IOMMU_DMA is enabled, you only support allocation
of DMA domains, not UNMANAGED domains anymore. Is there a reason for
that?

You can reduce the #ifdef'ed coded by supporting both types of domains
and call into allocation-subfunctions for DMA and UNMANAGED domains. The
#ifdef could then only let the dma-allocation function return NULL.

This would be much more compatible to what other IOMMU drivers do and
will allow VFIO usage in the future.



	Joerg