linux-kernel - Re: [PATCH v6 08/22] vfio: VFIO_IOMMU_CACHE

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Date:   Thu, 21 Mar 2019 16:43:00 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, joro@...tes.org,
        jacob.jun.pan@...ux.intel.com, yi.l.liu@...ux.intel.com,
        jean-philippe.brucker@....com, will.deacon@....com,
        robin.murphy@....com, kevin.tian@...el.com, ashok.raj@...el.com,
        marc.zyngier@....com, christoffer.dall@....com,
        peter.maydell@...aro.org, vincent.stehle@....com
Subject: Re: [PATCH v6 08/22] vfio: VFIO_IOMMU_CACHE_INVALIDATE

On Sun, 17 Mar 2019 18:22:18 +0100
Eric Auger <eric.auger@...hat.com> wrote:

> From: "Liu, Yi L" <yi.l.liu@...ux.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@...ux.intel.com>
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> 
> ---
> 
> 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 | 47 +++++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       | 13 +++++++++
>  2 files changed, 60 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 222e9199edbf..12a40b9db6aa 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -113,6 +113,26 @@ struct vfio_regions {
>  #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)	\
>  					(!list_empty(&iommu->domain_list))
>  

static struct foo {
	struct iommu_domain *domain;
	void *data;
};

> +/* iommu->lock must be held */
> +static int
> +vfio_iommu_for_each_dev(struct vfio_iommu *iommu, void *data,
> +			int (*fn)(struct device *, void *))
> +{
> +	struct vfio_domain *d;
> +	struct vfio_group *g;
> +	int ret = 0;

	struct foo bar = { .data = data };

> +
> +	list_for_each_entry(d, &iommu->domain_list, next) {

		bar.domain = d->domain;

> +		list_for_each_entry(g, &d->group_list, next) {
> +			ret = iommu_group_for_each_dev(g->iommu_group,
> +						       data, fn);

							s/data/&bar/

> +			if (ret)
> +				break;
> +		}
> +	}
> +	return ret;
> +}
> +
>  static int put_pfn(unsigned long pfn, int prot);
>  
>  /*
> @@ -1681,6 +1701,15 @@ vfio_attach_pasid_table(struct vfio_iommu *iommu,
>  	return ret;
>  }
>  
> +static int vfio_cache_inv_fn(struct device *dev, void *data)
> +{

struct foo *bar = data;

> +	struct vfio_iommu_type1_cache_invalidate *ustruct =
> +		(struct vfio_iommu_type1_cache_invalidate *)data;

... = bar->data;

> +	struct iommu_domain *d = iommu_get_domain_for_dev(dev);

... = bar->domain;

¯\_(ツ)_/¯ seems more efficient that doing a lookup.

> +
> +	return iommu_cache_invalidate(d, dev, &ustruct->info);
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>  				   unsigned int cmd, unsigned long arg)
>  {
> @@ -1767,6 +1796,24 @@ 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)
> +			return -EINVAL;
> +
> +		mutex_lock(&iommu->lock);
> +		ret = vfio_iommu_for_each_dev(iommu, &ustruct,
> +					      vfio_cache_inv_fn);

Guess what has a version field that never gets checked ;)

Thanks,
Alex

> +		mutex_unlock(&iommu->lock);
> +		return ret;
>  	}
>  
>  	return -ENOTTY;
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 329d378565d9..29f0ef2d805d 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -776,6 +776,19 @@ struct vfio_iommu_type1_attach_pasid_table {
>  #define VFIO_IOMMU_ATTACH_PASID_TABLE	_IO(VFIO_TYPE, VFIO_BASE + 22)
>  #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;
> +	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 -------- */
>  
>  /*