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

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