linux-kernel - Re: [PATCH v3 02/16] iommu: Introduce cache

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Message-ID: <44d5ba37-a9e9-cc7a-2a3a-d32b840afa29@arm.com>
Date:   Mon, 13 May 2019 12:20:27 +0100
From:   Jean-Philippe Brucker <jean-philippe.brucker@....com>
To:     Auger Eric <eric.auger@...hat.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     Yi Liu <yi.l.liu@...el.com>, "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Andriy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v3 02/16] iommu: Introduce cache_invalidate API

Hi Eric,

On 13/05/2019 10:14, Auger Eric wrote:
> I noticed my qemu integration was currently incorrectly using PASID
> invalidation for ASID based invalidation (SMMUV3 Stage1 CMD_TLBI_NH_ASID
> invalidation command). So I think we also need ARCHID invalidation.
> Sorry for the late notice.
>>  
>> +/* defines the granularity of the invalidation */
>> +enum iommu_inv_granularity {
>> +	IOMMU_INV_GRANU_DOMAIN,	/* domain-selective invalidation */
>         IOMMU_INV_GRANU_ARCHID, /* archid-selective invalidation */
>> +	IOMMU_INV_GRANU_PASID,	/* pasid-selective invalidation */

In terms of granularity, these values have the same meaning: invalidate
the whole address space of a context. Then you can communicate two
things using the same struct:
* If ATS is enables an Arm host needs to invalidate all ATC entries
using PASID.
* If BTM isn't used by the guest, the host needs to invalidate all TLB
entries using ARCHID.

Rather than introducing a new granule here, could we just add an archid
field to the struct associated with IOMMU_INV_GRANU_PASID? Something like...

>> +	IOMMU_INV_GRANU_ADDR,	/* page-selective invalidation */
>> +	IOMMU_INVAL_GRANU_NR,   /* number of invalidation granularities */
>> +};
>> +
>> +/**
>> + * Address Selective Invalidation Structure
>> + *
>> + * @flags indicates the granularity of the address-selective invalidation
>> + * - if PASID bit is set, @pasid field is populated and the invalidation
>> + *   relates to cache entries tagged with this PASID and matching the
>> + *   address range.
>> + * - if ARCHID bit is set, @archid is populated and the invalidation relates
>> + *   to cache entries tagged with this architecture specific id and matching
>> + *   the address range.
>> + * - Both PASID and ARCHID can be set as they may tag different caches.
>> + * - if neither PASID or ARCHID is set, global addr invalidation applies
>> + * - LEAF flag indicates whether only the leaf PTE caching needs to be
>> + *   invalidated and other paging structure caches can be preserved.
>> + * @pasid: process address space id
>> + * @archid: architecture-specific id
>> + * @addr: first stage/level input address
>> + * @granule_size: page/block size of the mapping in bytes
>> + * @nb_granules: number of contiguous granules to be invalidated
>> + */
>> +struct iommu_inv_addr_info {
>> +#define IOMMU_INV_ADDR_FLAGS_PASID	(1 << 0)
>> +#define IOMMU_INV_ADDR_FLAGS_ARCHID	(1 << 1)
>> +#define IOMMU_INV_ADDR_FLAGS_LEAF	(1 << 2)
>> +	__u32	flags;
>> +	__u32	archid;
>> +	__u64	pasid;
>> +	__u64	addr;
>> +	__u64	granule_size;
>> +	__u64	nb_granules;
>> +};

struct iommu_inv_pasid_info {
#define IOMMU_INV_PASID_FLAGS_PASID	(1 << 0)
#define IOMMU_INV_PASID_FLAGS_ARCHID	(1 << 1)
	__u32	flags;
	__u32	archid;
	__u64	pasid;
};

>> +
>> +/**
>> + * First level/stage invalidation information
>> + * @cache: bitfield that allows to select which caches to invalidate
>> + * @granularity: defines the lowest granularity used for the invalidation:
>> + *     domain > pasid > addr
>> + *
>> + * Not all the combinations of cache/granularity make sense:
>> + *
>> + *         type |   DEV_IOTLB   |     IOTLB     |      PASID    |
>> + * granularity	|		|		|      cache	|
>> + * -------------+---------------+---------------+---------------+
>> + * DOMAIN	|	N/A	|       Y	|	Y	|
>  * ARCHID       |       N/A     |       Y       |       N/A     |
> 
>> + * PASID	|	Y	|       Y	|	Y	|
>> + * ADDR		|       Y	|       Y	|	N/A	|
>> + *
>> + * Invalidations by %IOMMU_INV_GRANU_ADDR use field @addr_info.
>  * Invalidations by %IOMMU_INV_GRANU_ARCHID use field @archid.
>> + * Invalidations by %IOMMU_INV_GRANU_PASID use field @pasid.
>> + * Invalidations by %IOMMU_INV_GRANU_DOMAIN don't take any argument.
>> + *
>> + * If multiple cache types are invalidated simultaneously, they all
>> + * must support the used granularity.
>> + */
>> +struct iommu_cache_invalidate_info {
>> +#define IOMMU_CACHE_INVALIDATE_INFO_VERSION_1 1
>> +	__u32	version;
>> +/* IOMMU paging structure cache */
>> +#define IOMMU_CACHE_INV_TYPE_IOTLB	(1 << 0) /* IOMMU IOTLB */
>> +#define IOMMU_CACHE_INV_TYPE_DEV_IOTLB	(1 << 1) /* Device IOTLB */
>> +#define IOMMU_CACHE_INV_TYPE_PASID	(1 << 2) /* PASID cache */
>> +#define IOMMU_CACHE_TYPE_NR		(3)
>> +	__u8	cache;
>> +	__u8	granularity;
>> +	__u8	padding[2];
>> +	union {
>> +		__u64	pasid;
>                 __u32   archid;

struct iommu_inv_pasid_info pasid_info;

Thanks,
Jean

> 
> Thanks
> 
> Eric
>> +		struct iommu_inv_addr_info addr_info;
>> +	};
>> +};
>> +
>> +
>>  #endif /* _UAPI_IOMMU_H */
>>