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

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Message-ID: <109c3520-dd26-3c0b-35d1-48b169fea982@arm.com>
Date:   Thu, 21 Mar 2019 14:13:22 +0000
From:   Jean-Philippe Brucker <jean-philippe.brucker@....com>
To:     Auger Eric <eric.auger@...hat.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     yi.l.liu@...ux.intel.com, kevin.tian@...el.com,
        vincent.stehle@....com, ashok.raj@...el.com, kvm@...r.kernel.org,
        peter.maydell@...aro.org, marc.zyngier@....com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, christoffer.dall@....com,
        alex.williamson@...hat.com, robin.murphy@....com,
        kvmarm@...ts.cs.columbia.edu, eric.auger.pro@...il.com
Subject: Re: [PATCH v6 05/22] iommu: Introduce cache_invalidate API

On 21/03/2019 13:54, Auger Eric wrote:
> 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:

My mistake: I meant dev-IOTLB and domain granularity are N/A

Thanks,
Jean

> "
> • 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
>>>
>>
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>

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