linux-kernel - Re: [PATCH v7 03/10] iommu/sva: Add iommu_sva

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Date:   Mon, 23 May 2022 15:12:53 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>, Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>
Cc:     baolu.lu@...ux.intel.com, Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [PATCH v7 03/10] iommu/sva: Add iommu_sva_domain support

On 2022/5/19 15:20, Lu Baolu wrote:
> The iommu_sva_domain represents a hardware pagetable that the IOMMU
> hardware could use for SVA translation. This adds some infrastructure
> to support SVA domain in the iommu common layer. It includes:
> 
> - Add a new struct iommu_sva_domain and new IOMMU_DOMAIN_SVA domain
>    type.
> - Add a new domain ops pointer in iommu_ops. The IOMMU drivers that
>    support SVA should provide the callbacks.
> - Add helpers to allocate and free an SVA domain.
> - Add helpers to set an SVA domain to a device and the reverse
>    operation.
> 
> Some buses, like PCI, route packets without considering the PASID value.
> Thus a DMA target address with PASID might be treated as P2P if the
> address falls into the MMIO BAR of other devices in the group. To make
> things simple, the attach/detach interfaces only apply to devices
> belonging to the singleton groups, and the singleton is immutable in
> fabric i.e. not affected by hotplug.
> 
> The iommu_set/block_device_pasid() can be used for other purposes,
> such as kernel DMA with pasid, mediation device, etc. Hence, it is put
> in the iommu.c.
> 
> Suggested-by: Jean-Philippe Brucker<jean-philippe@...aro.org>
> Suggested-by: Jason Gunthorpe<jgg@...dia.com>
> Signed-off-by: Lu Baolu<baolu.lu@...ux.intel.com>
> ---
>   include/linux/iommu.h         | 51 +++++++++++++++++++++++++
>   drivers/iommu/iommu-sva-lib.h | 15 ++++++++
>   drivers/iommu/iommu-sva-lib.c | 48 +++++++++++++++++++++++
>   drivers/iommu/iommu.c         | 71 +++++++++++++++++++++++++++++++++++
>   4 files changed, 185 insertions(+)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 0c358b7c583b..e8cf82d46ce1 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -64,6 +64,9 @@ struct iommu_domain_geometry {
>   #define __IOMMU_DOMAIN_PT	(1U << 2)  /* Domain is identity mapped   */
>   #define __IOMMU_DOMAIN_DMA_FQ	(1U << 3)  /* DMA-API uses flush queue    */
>   
> +#define __IOMMU_DOMAIN_SHARED	(1U << 4)  /* Page table shared from CPU  */
> +#define __IOMMU_DOMAIN_HOST_VA	(1U << 5)  /* Host CPU virtual address */
> +
>   /*
>    * This are the possible domain-types
>    *
> @@ -86,6 +89,8 @@ struct iommu_domain_geometry {
>   #define IOMMU_DOMAIN_DMA_FQ	(__IOMMU_DOMAIN_PAGING |	\
>   				 __IOMMU_DOMAIN_DMA_API |	\
>   				 __IOMMU_DOMAIN_DMA_FQ)
> +#define IOMMU_DOMAIN_SVA	(__IOMMU_DOMAIN_SHARED |	\
> +				 __IOMMU_DOMAIN_HOST_VA)
>   
>   struct iommu_domain {
>   	unsigned type;
> @@ -254,6 +259,7 @@ struct iommu_ops {
>   	int (*def_domain_type)(struct device *dev);
>   
>   	const struct iommu_domain_ops *default_domain_ops;
> +	const struct iommu_domain_ops *sva_domain_ops;

Per Joerg's comment in anther thread,

https://lore.kernel.org/linux-iommu/YodVJ7ervpIdWfg+@8bytes.org/

adding a sva_domain_ops here is not the right way to go.

If no objection, I will make the sva domain go through the
generic domain_alloc/free() callbacks in the next version.

Best regards,
baolu