linux-kernel - Re: [PATCH v13 02/15] iommu/arm-smmu: Initialize the msi geometry

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Date:   Thu, 6 Oct 2016 14:16:48 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, christoffer.dall@...aro.org,
        marc.zyngier@....com, robin.murphy@....com, will.deacon@....com,
        joro@...tes.org, tglx@...utronix.de, jason@...edaemon.net,
        linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org,
        drjones@...hat.com, linux-kernel@...r.kernel.org,
        Bharat.Bhushan@...escale.com, pranav.sawargaonkar@...il.com,
        p.fedin@...sung.com, iommu@...ts.linux-foundation.org,
        Jean-Philippe.Brucker@....com, yehuday@...vell.com,
        Manish.Jaggi@...iumnetworks.com
Subject: Re: [PATCH v13 02/15] iommu/arm-smmu: Initialize the msi geometry

On Thu,  6 Oct 2016 08:45:18 +0000
Eric Auger <eric.auger@...hat.com> wrote:

> On ARM, MSI write transactions also are translated by the smmu.
> Let's report that specificity by setting the iommu_msi_supported
> field to true. A valid aperture window will need to be provided.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> 
> ---
> v12 -> v13:
> - reword the commit message
> 
> v8 -> v9:
> - reword the title and patch description
> 
> v7 -> v8:
> - use DOMAIN_ATTR_MSI_GEOMETRY
> 
> v4 -> v5:
> - don't handle fsl_pamu_domain anymore
> - handle arm-smmu-v3
> ---
>  drivers/iommu/arm-smmu-v3.c | 2 ++
>  drivers/iommu/arm-smmu.c    | 3 +++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 15c01c3..f82eec3 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -1382,6 +1382,7 @@ static bool arm_smmu_capable(enum iommu_cap cap)
>  static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
>  {
>  	struct arm_smmu_domain *smmu_domain;
> +	struct iommu_domain_msi_geometry msi_geometry = {0, 0, true};

nit, this initialization makes it difficult to search for who sets
iommu_msi_supported, could we perhaps be more explicit in the
initialization, ie.
	{
		.aperture_start = 0,
		.aperture_end = 0,
		.iommu_msi_supported = true
	};

No change to the compiled version, but easier to find in the source.

>  
>  	if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
>  		return NULL;
> @@ -1400,6 +1401,7 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
>  		kfree(smmu_domain);
>  		return NULL;
>  	}
> +	smmu_domain->domain.msi_geometry = msi_geometry;
>  
>  	mutex_init(&smmu_domain->init_mutex);
>  	spin_lock_init(&smmu_domain->pgtbl_lock);
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index ac4aab9..97ff1b4 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1002,6 +1002,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
>  static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
>  {
>  	struct arm_smmu_domain *smmu_domain;
> +	struct iommu_domain_msi_geometry msi_geometry = {0, 0, true};
>  
>  	if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
>  		return NULL;
> @@ -1020,6 +1021,8 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
>  		return NULL;
>  	}
>  
> +	smmu_domain->domain.msi_geometry = msi_geometry;
> +
>  	mutex_init(&smmu_domain->init_mutex);
>  	spin_lock_init(&smmu_domain->pgtbl_lock);
>