Re: [RFC v3 02/21] iommu: Introduce cache_invalidate API

[Alex Williamson <alex.williamson@redhat.com>]

On Tue,  8 Jan 2019 11:26:14 +0100
Eric Auger <eric.auger@redhat.com> wrote:

> From: "Liu, Yi L" <yi.l.liu@linux.intel.com>
> 
> In any virtualization use case, when the first translation stage
> is "owned" by the guest OS, the host IOMMU driver has no knowledge
> of caching structure updates unless the guest invalidation activities
> are trapped by the virtualizer and passed down to the host.
> 
> Since the invalidation data are obtained from user space and will be
> written into physical IOMMU, we must allow security check at various
> layers. Therefore, generic invalidation data format are proposed here,
> model specific IOMMU drivers need to convert them into their own format.
> 
> Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Ashok Raj <ashok.raj@intel.com>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> ---
> v1 -> v2:
> - add arch_id field
> - renamed tlb_invalidate into cache_invalidate as this API allows
>   to invalidate context caches on top of IOTLBs
> 
> v1:
> renamed sva_invalidate into tlb_invalidate and add iommu_ prefix in
> header. Commit message reworded.
> ---
>  drivers/iommu/iommu.c      | 14 ++++++
>  include/linux/iommu.h      | 14 ++++++
>  include/uapi/linux/iommu.h | 95 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 123 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 0f2b7f1fc7c8..b2e248770508 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1403,6 +1403,20 @@ int iommu_set_pasid_table(struct iommu_domain *domain,
>  }
>  EXPORT_SYMBOL_GPL(iommu_set_pasid_table);
>  
> +int iommu_cache_invalidate(struct iommu_domain *domain, struct device *dev,
> +			   struct iommu_cache_invalidate_info *inv_info)
> +{
> +	int ret = 0;
> +
> +	if (unlikely(!domain->ops->cache_invalidate))
> +		return -ENODEV;
> +
> +	ret = domain->ops->cache_invalidate(domain, dev, inv_info);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_cache_invalidate);
> +
>  static void __iommu_detach_device(struct iommu_domain *domain,
>  				  struct device *dev)
>  {
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 1da2a2357ea4..96d59886f230 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -186,6 +186,7 @@ struct iommu_resv_region {
>   * @of_xlate: add OF master IDs to iommu grouping
>   * @pgsize_bitmap: bitmap of all possible supported page sizes
>   * @set_pasid_table: set pasid table
> + * @cache_invalidate: invalidate translation caches
>   */
>  struct iommu_ops {
>  	bool (*capable)(enum iommu_cap);
> @@ -231,6 +232,9 @@ struct iommu_ops {
>  	int (*set_pasid_table)(struct iommu_domain *domain,
>  			       struct iommu_pasid_table_config *cfg);
>  
> +	int (*cache_invalidate)(struct iommu_domain *domain, struct device *dev,
> +				struct iommu_cache_invalidate_info *inv_info);
> +
>  	unsigned long pgsize_bitmap;
>  };
>  
> @@ -294,6 +298,9 @@ extern void iommu_detach_device(struct iommu_domain *domain,
>  				struct device *dev);
>  extern int iommu_set_pasid_table(struct iommu_domain *domain,
>  				 struct iommu_pasid_table_config *cfg);
> +extern int iommu_cache_invalidate(struct iommu_domain *domain,
> +				struct device *dev,
> +				struct iommu_cache_invalidate_info *inv_info);
>  extern struct iommu_domain *iommu_get_domain_for_dev(struct device *dev);
>  extern struct iommu_domain *iommu_get_dma_domain(struct device *dev);
>  extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
> @@ -709,6 +716,13 @@ int iommu_set_pasid_table(struct iommu_domain *domain,
>  {
>  	return -ENODEV;
>  }
> +static inline int
> +iommu_cache_invalidate(struct iommu_domain *domain,
> +		       struct device *dev,
> +		       struct iommu_cache_invalidate_info *inv_info)
> +{
> +	return -ENODEV;
> +}
>  
>  #endif /* CONFIG_IOMMU_API */
>  
> diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
> index 7a7cf7a3de7c..4605f5cfac84 100644
> --- a/include/uapi/linux/iommu.h
> +++ b/include/uapi/linux/iommu.h
> @@ -47,4 +47,99 @@ struct iommu_pasid_table_config {
>  	};
>  };
>  
> +/**
> + * enum iommu_inv_granularity - Generic invalidation granularity
> + * @IOMMU_INV_GRANU_DOMAIN_ALL_PASID:	TLB entries or PASID caches of all
> + *					PASIDs associated with a domain ID
> + * @IOMMU_INV_GRANU_PASID_SEL:		TLB entries or PASID cache associated
> + *					with a PASID and a domain
> + * @IOMMU_INV_GRANU_PAGE_PASID:		TLB entries of selected page range
> + *					within a PASID
> + *
> + * When an invalidation request is passed down to IOMMU to flush translation
> + * caches, it may carry different granularity levels, which can be specific
> + * to certain types of translation caches.
> + * This enum is a collection of granularities for all types of translation
> + * caches. The idea is to make it easy for IOMMU model specific driver to
> + * convert from generic to model specific value. Each IOMMU driver
> + * can enforce check based on its own conversion table. The conversion is
> + * based on 2D look-up with inputs as follows:
> + * - translation cache types
> + * - granularity
> + *
> + *             type |   DTLB    |    TLB    |   PASID   |
> + *  granule         |           |           |   cache   |
> + * -----------------+-----------+-----------+-----------+
> + *  DN_ALL_PASID    |   Y       |   Y       |   Y       |
> + *  PASID_SEL       |   Y       |   Y       |   Y       |
> + *  PAGE_PASID      |   Y       |   Y       |   N/A     |
> + *
> + */
> +enum iommu_inv_granularity {
> +	IOMMU_INV_GRANU_DOMAIN_ALL_PASID,
> +	IOMMU_INV_GRANU_PASID_SEL,
> +	IOMMU_INV_GRANU_PAGE_PASID,
> +	IOMMU_INV_NR_GRANU,
> +};
> +
> +/**
> + * enum iommu_inv_type - Generic translation cache types for invalidation
> + *
> + * @IOMMU_INV_TYPE_DTLB:	device IOTLB
> + * @IOMMU_INV_TYPE_TLB:		IOMMU paging structure cache
> + * @IOMMU_INV_TYPE_PASID:	PASID cache
> + * Invalidation requests sent to IOMMU for a given device need to indicate
> + * which type of translation cache to be operated on. Combined with enum
> + * iommu_inv_granularity, model specific driver can do a simple lookup to
> + * convert from generic to model specific value.
> + */
> +enum iommu_inv_type {
> +	IOMMU_INV_TYPE_DTLB,
> +	IOMMU_INV_TYPE_TLB,
> +	IOMMU_INV_TYPE_PASID,
> +	IOMMU_INV_NR_TYPE
> +};
> +
> +/**
> + * Translation cache invalidation header that contains mandatory meta data.
> + * @version:	info format version, expecting future extesions
> + * @type:	type of translation cache to be invalidated
> + */
> +struct iommu_cache_invalidate_hdr {
> +	__u32 version;
> +#define TLB_INV_HDR_VERSION_1 1
> +	enum iommu_inv_type type;
> +};
> +
> +/**
> + * Translation cache invalidation information, contains generic IOMMU
> + * data which can be parsed based on model ID by model specific drivers.
> + * Since the invalidation of second level page tables are included in the
> + * unmap operation, this info is only applicable to the first level
> + * translation caches, i.e. DMA request with PASID.
> + *
> + * @granularity:	requested invalidation granularity, type dependent
> + * @size:		2^size of 4K pages, 0 for 4k, 9 for 2MB, etc.

Why is this a 4K page centric interface?

> + * @nr_pages:		number of pages to invalidate
> + * @pasid:		processor address space ID value per PCI spec.
> + * @arch_id:		architecture dependent id characterizing a context
> + *			and tagging the caches, ie. domain Identfier on VTD,
> + *			asid on ARM SMMU
> + * @addr:		page address to be invalidated
> + * @flags		IOMMU_INVALIDATE_ADDR_LEAF: leaf paging entries
> + *			IOMMU_INVALIDATE_GLOBAL_PAGE: global pages

Shouldn't some of these be tied the the granularity of the
invalidation?  It seems like this should be more similar to
iommu_pasid_table_config where the granularity of the invalidation
defines which entry within a union at the end of the structure is valid
and populated.  Otherwise we have fields that don't make sense for
certain invalidations.

> + *
> + */
> +struct iommu_cache_invalidate_info {
> +	struct iommu_cache_invalidate_hdr	hdr;
> +	enum iommu_inv_granularity	granularity;

A separate structure for hdr seems a little pointless.

> +	__u32		flags;
> +#define IOMMU_INVALIDATE_ADDR_LEAF	(1 << 0)
> +#define IOMMU_INVALIDATE_GLOBAL_PAGE	(1 << 1)
> +	__u8		size;

Really need some padding or packing here for any hope of having
consistency with userspace.

> +	__u64		nr_pages;
> +	__u32		pasid;

Sub-optimal ordering for packing/padding.  Thanks,

Alex

> +	__u64		arch_id;
> +	__u64		addr;
> +};
>  #endif /* _UAPI_IOMMU_H */