Re: [PATCH v7 01/10] iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute

From	Robin Murphy <robin.murphy@arm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v7 01/10] iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute
Date	2016-04-20 14:50 +0200
Message-ID	<rpZJV-7YC-35@gated-at.bofh.it> (permalink)
References	<rpHah-1sn-3@gated-at.bofh.it> <rpHai-1sn-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi Eric,

On 19/04/16 17:56, Eric Auger wrote:
> Introduce a new DOMAIN_ATTR_MSI_MAPPING domain attribute. If supported,
> this means the MSI addresses need to be mapped in the IOMMU.
>
> x86 IOMMUs typically don't expose the attribute since on x86, MSI write
> transaction addresses always are within the 1MB PA region [FEE0_0000h -
> FEF0_000h] window which directly targets the APIC configuration space and
> hence bypass the sMMU. On ARM and PowerPC however MSI transactions are
> conveyed through the IOMMU.

What's stopping us from simply inferring this from the domain's IOMMU 
not advertising interrupt remapping capabilities?

Robin.

> Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com>
> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>
> ---
>
> v4 -> v5:
> - introduce the user in the next patch
>
> RFC v1 -> v1:
> - the data field is not used
> - for this attribute domain_get_attr simply returns 0 if the MSI_MAPPING
>    capability if needed or <0 if not.
> - removed struct iommu_domain_msi_maps
> ---
>   include/linux/iommu.h | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 62a5eae..b3e8c5b 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -113,6 +113,7 @@ enum iommu_attr {
>   	DOMAIN_ATTR_FSL_PAMU_ENABLE,
>   	DOMAIN_ATTR_FSL_PAMUV1,
>   	DOMAIN_ATTR_NESTING,	/* two stages of translation */
> +	DOMAIN_ATTR_MSI_MAPPING, /* Require MSIs mapping in iommu */
>   	DOMAIN_ATTR_MAX,
>   };
>
>

Thread

[PATCH v7 01/10] iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute Eric Auger <eric.auger@linaro.org> - 2016-04-19 19:00 +0200
  Re: [PATCH v7 01/10] iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute Robin Murphy <robin.murphy@arm.com> - 2016-04-20 14:50 +0200
    Re: [PATCH v7 01/10] iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute Eric Auger <eric.auger@linaro.org> - 2016-04-20 18:10 +0200
      Re: [PATCH v7 01/10] iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute Robin Murphy <robin.murphy@arm.com> - 2016-04-22 13:40 +0200
        Re: [PATCH v7 01/10] iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute Eric Auger <eric.auger@linaro.org> - 2016-04-22 14:10 +0200
          Re: [PATCH v7 01/10] iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute Robin Murphy <robin.murphy@arm.com> - 2016-04-22 17:00 +0200
            Re: [PATCH v7 01/10] iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute Eric Auger <eric.auger@linaro.org> - 2016-04-22 17:40 +0200

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