linux-kernel - Re: [PATCH v6 05/22] iommu: Introduce cache_invalidate API

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Message-ID: <ad4d18ec-0040-901f-8d37-0fccb3cfd0d5@redhat.com>
Date:   Thu, 21 Mar 2019 14:54:26 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     yi.l.liu@...ux.intel.com, kevin.tian@...el.com,
        vincent.stehle@....com, alex.williamson@...hat.com,
        ashok.raj@...el.com, kvm@...r.kernel.org, peter.maydell@...aro.org,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        christoffer.dall@....com, marc.zyngier@....com,
        iommu@...ts.linux-foundation.org, robin.murphy@....com,
        kvmarm@...ts.cs.columbia.edu, eric.auger.pro@...il.com
Subject: Re: [PATCH v6 05/22] iommu: Introduce cache_invalidate API

Hi Jacob, Jean-Philippe,

On 3/20/19 5:50 PM, Jean-Philippe Brucker wrote:
> On 20/03/2019 16:37, Jacob Pan wrote:
> [...]
>>> +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;
>>> +};
>>> +
>>> +/**
>>> + * 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	|
>>> + * PASID	|	Y	|       Y	|
>>> Y	|
>>> + * ADDR		|       Y	|       Y	|
>>> N/A	|
>>> + */
>>> +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 */
>> Just a clarification, this used to be an enum. You do intend to issue a
>> single invalidation request on multiple cache types? Perhaps for
>> virtio-IOMMU? I only see a single cache type in your patch #14. For VT-d
>> we plan to issue one cache type at a time for now. So this format works
>> for us.
> 
> Yes for virtio-iommu I'd like as little overhead as possible, which
> means a single invalidation message to hit both IOTLB and ATC at once,
> and the ability to specify multiple pages with @nb_granules.
The original request/explanation from Jean-Philippe can be found here:
https://lkml.org/lkml/2019/1/28/1497

> 
>> However, if multiple cache types are issued in a single invalidation.
>> They must share a single granularity, not all combinations are valid.
>> e.g. dev IOTLB does not support domain granularity. Just a reminder,
>> not an issue. Driver could filter out invalid combinations.
Sure I will add a comment about this restriction.
> 
> Agreed. Even the core could filter out invalid combinations based on the
> table above: IOTLB and domain granularity are N/A.
I don't get this sentence. What about vtd IOTLB domain-selective
invalidation:
"
• IOTLB entries caching mappings associated with the specified domain-id
are invalidated.
• Paging-structure-cache entries caching mappings associated with the
specified domain-id are invalidated.
"

Thanks

Eric

> 
> Thanks,
> Jean
> 
>>
>>> +	__u8	cache;
>>> +	__u8	granularity;
>>> +	__u8	padding[2];
>>> +	union {
>>> +		__u64	pasid;
>>> +		struct iommu_inv_addr_info addr_info;
>>> +	};
>>> +};
>>> +
>>> +
>>>  #endif /* _UAPI_IOMMU_H */
>>
>> [Jacob Pan]
>> _______________________________________________
>> iommu mailing list
>> iommu@...ts.linux-foundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>>
> 

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