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

From: Jean-Philippe Brucker
Date: Wed Mar 20 2019 - 12:50:30 EST


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.

> 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.

Agreed. Even the core could filter out invalid combinations based on the
table above: IOTLB and domain granularity are N/A.

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]
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