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

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Date:   Thu, 21 Mar 2019 15:32:45 +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, 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

Hi jean, Jacob,

On 3/21/19 3:13 PM, Jean-Philippe Brucker wrote:
> 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

Ah OK, no worries.

How do we proceed further with those user APIs? Besides the comment to
be added above and previous suggestion from Jean ("Invalidations by
@granularity use field ...), have we reached a consensus now on:

- attach/detach_pasid_table
- cache_invalidate
- fault data and fault report API?

If not, please let me know.

Thanks

Eric

> 
> 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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