Re: [PATCH v8 23/29] vfio: VFIO_IOMMU_CACHE_INVALIDATE

[Auger Eric <eric.auger@redhat.com>]

Hi Liu,

On 6/14/19 2:38 PM, Liu, Yi L wrote:
> Hi Eric,
> 
>> From: Eric Auger [mailto:eric.auger@redhat.com]
>> Sent: Monday, May 27, 2019 12:10 AM
>> Subject: [PATCH v8 23/29] vfio: VFIO_IOMMU_CACHE_INVALIDATE
>>
>> From: "Liu, Yi L" <yi.l.liu@linux.intel.com>
>>
>> When the guest "owns" the stage 1 translation structures,  the host IOMMU driver
>> has no knowledge of caching structure updates unless the guest invalidation
>> requests are trapped and passed down to the host.
>>
>> This patch adds the VFIO_IOMMU_CACHE_INVALIDATE ioctl with aims at
>> propagating guest stage1 IOMMU cache invalidations to the host.
>>
>> Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>
>> ---
>> v6 -> v7:
>> - Use iommu_capsule struct
>> - renamed vfio_iommu_for_each_dev into vfio_iommu_lookup_dev
>>   due to checkpatch error related to for_each_dev suffix
>>
>> v2 -> v3:
>> - introduce vfio_iommu_for_each_dev back in this patch
>>
>> v1 -> v2:
>> - s/TLB/CACHE
>> - remove vfio_iommu_task usage
>> - commit message rewording
>> ---
>>  drivers/vfio/vfio_iommu_type1.c | 55 +++++++++++++++++++++++++++++++++
>>  include/uapi/linux/vfio.h       | 13 ++++++++
>>  2 files changed, 68 insertions(+)
>>
>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>> index b2d609d6fe83..6fda4fbc9bfa 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -120,6 +120,34 @@ struct vfio_regions {
>>  #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)	\
>>  					(!list_empty(&iommu->domain_list))
>>
>> +struct domain_capsule {
>> +	struct iommu_domain *domain;
>> +	void *data;
>> +};
>> +
>> +/* iommu->lock must be held */
>> +static int
>> +vfio_iommu_lookup_dev(struct vfio_iommu *iommu,
>> +		      int (*fn)(struct device *dev, void *data),
>> +		      void *data)
>> +{
>> +	struct domain_capsule dc = {.data = data};
>> +	struct vfio_domain *d;
>> +	struct vfio_group *g;
>> +	int ret = 0;
>> +
>> +	list_for_each_entry(d, &iommu->domain_list, next) {
>> +		dc.domain = d->domain;
>> +		list_for_each_entry(g, &d->group_list, next) {
>> +			ret = iommu_group_for_each_dev(g->iommu_group,
>> +						       &dc, fn);
>> +			if (ret)
>> +				break;
>> +		}
>> +	}
>> +	return ret;
>> +}
>> +
>>  static int put_pfn(unsigned long pfn, int prot);
>>
>>  /*
>> @@ -1795,6 +1823,15 @@ vfio_attach_pasid_table(struct vfio_iommu *iommu,
>>  	return ret;
>>  }
>>
>> +static int vfio_cache_inv_fn(struct device *dev, void *data) {
>> +	struct domain_capsule *dc = (struct domain_capsule *)data;
>> +	struct vfio_iommu_type1_cache_invalidate *ustruct =
>> +		(struct vfio_iommu_type1_cache_invalidate *)dc->data;
>> +
>> +	return iommu_cache_invalidate(dc->domain, dev, &ustruct->info); }
>> +
>>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>>  				   unsigned int cmd, unsigned long arg)  { @@ -
>> 1881,6 +1918,24 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>>  	} else if (cmd == VFIO_IOMMU_DETACH_PASID_TABLE) {
>>  		vfio_detach_pasid_table(iommu);
>>  		return 0;
>> +	} else if (cmd == VFIO_IOMMU_CACHE_INVALIDATE) {
>> +		struct vfio_iommu_type1_cache_invalidate ustruct;
>> +		int ret;
>> +
>> +		minsz = offsetofend(struct vfio_iommu_type1_cache_invalidate,
>> +				    info);
>> +
>> +		if (copy_from_user(&ustruct, (void __user *)arg, minsz))
>> +			return -EFAULT;
>> +
>> +		if (ustruct.argsz < minsz || ustruct.flags)
> 
> May remove the flags field?
> 
>> +			return -EINVAL;
>> +
>> +		mutex_lock(&iommu->lock);
>> +		ret = vfio_iommu_lookup_dev(iommu, vfio_cache_inv_fn,
>> +					    &ustruct);
>> +		mutex_unlock(&iommu->lock);
>> +		return ret;
>>  	}
>>
>>  	return -ENOTTY;
>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h index
>> 4316dd8cb5b5..055aa9b9745a 100644
>> --- a/include/uapi/linux/vfio.h
>> +++ b/include/uapi/linux/vfio.h
>> @@ -785,6 +785,19 @@ struct vfio_iommu_type1_attach_pasid_table {
>>   */
>>  #define VFIO_IOMMU_DETACH_PASID_TABLE	_IO(VFIO_TYPE, VFIO_BASE + 23)
>>
>> +/**
>> + * VFIO_IOMMU_CACHE_INVALIDATE - _IOWR(VFIO_TYPE, VFIO_BASE + 24,
>> + *			struct vfio_iommu_type1_cache_invalidate)
>> + *
>> + * Propagate guest IOMMU cache invalidation to the host.
>> + */
>> +struct vfio_iommu_type1_cache_invalidate {
>> +	__u32   argsz;
>> +	__u32   flags;
> 
> Looks like there is no more usage on "flags". is it?

Agreed. However all the other vfio structs embed it.
vfio_iommu_type1_dma_unmap (VFIO_IOMMU_UNMAP_DMA) or
vfio_iommu_type1_info (VFIO_IOMMU_GET_INFO) also feature it and do not
use it either if I am not wrong.

So I guess flags is a common pattern for the API and somehow allows to
extend the API if needed. So I would be inclined to keep it, no?

Thanks

Eric
> 
> Regards,
> Yi Liu
> 
>> +	struct iommu_cache_invalidate_info info; };
>> +#define VFIO_IOMMU_CACHE_INVALIDATE      _IO(VFIO_TYPE, VFIO_BASE + 24)
>> +
>>  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
>>
>>  /*
>> --
>> 2.20.1
> 
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