RE: [PATCH v3 09/14] vfio/type1: Support binding guest page tables to PASID

["Liu, Yi L" <yi.l.liu@intel.com>]

Hi Alex,

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Friday, July 3, 2020 5:20 AM
> 
> On Wed, 24 Jun 2020 01:55:22 -0700
> Liu Yi L <yi.l.liu@intel.com> wrote:
> 
> > Nesting translation allows two-levels/stages page tables, with 1st
> > level for guest translations (e.g. GVA->GPA), 2nd level for host
> > translations (e.g. GPA->HPA). This patch adds interface for binding
> > guest page tables to a PASID. This PASID must have been allocated to
> > user space before the binding request.
> >
> > Cc: Kevin Tian <kevin.tian@intel.com>
> > CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Cc: Alex Williamson <alex.williamson@redhat.com>
> > Cc: Eric Auger <eric.auger@redhat.com>
> > Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > Cc: Joerg Roedel <joro@8bytes.org>
> > Cc: Lu Baolu <baolu.lu@linux.intel.com>
> > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.com>
> > Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> > v2 -> v3:
> > *) use __iommu_sva_unbind_gpasid() for unbind call issued by VFIO
> > https://lore.kernel.org/linux-iommu/1592931837-58223-6-git-send-email-
> > jacob.jun.pan@linux.intel.com/
> >
> > v1 -> v2:
> > *) rename subject from "vfio/type1: Bind guest page tables to host"
> > *) remove VFIO_IOMMU_BIND, introduce VFIO_IOMMU_NESTING_OP to
> support bind/
> >    unbind guet page table
> > *) replaced vfio_iommu_for_each_dev() with a group level loop since this
> >    series enforces one group per container w/ nesting type as start.
> > *) rename vfio_bind/unbind_gpasid_fn() to
> > vfio_dev_bind/unbind_gpasid_fn()
> > *) vfio_dev_unbind_gpasid() always successful
> > *) use vfio_mm->pasid_lock to avoid race between PASID free and page table
> >    bind/unbind
> > ---
> >  drivers/vfio/vfio_iommu_type1.c | 169
> ++++++++++++++++++++++++++++++++++++++++
> >  drivers/vfio/vfio_pasid.c       |  30 +++++++
> >  include/linux/vfio.h            |  20 +++++
> >  include/uapi/linux/vfio.h       |  30 +++++++
> >  4 files changed, 249 insertions(+)
> >
> > diff --git a/drivers/vfio/vfio_iommu_type1.c
> > b/drivers/vfio/vfio_iommu_type1.c index d0891c5..5926533 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c
> > @@ -148,6 +148,33 @@ struct vfio_regions {
> >  #define DIRTY_BITMAP_PAGES_MAX	 ((u64)INT_MAX)
> >  #define DIRTY_BITMAP_SIZE_MAX
> DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
> >
> > +struct domain_capsule {
> > +	struct vfio_group *group;
> > +	struct iommu_domain *domain;
> > +	void *data;
> > +};
> > +
> > +/* iommu->lock must be held */
> > +static struct vfio_group *vfio_find_nesting_group(struct vfio_iommu
> > +*iommu) {
> > +	struct vfio_domain *d;
> > +	struct vfio_group *g, *group = NULL;
> > +
> > +	if (!iommu->nesting_info)
> > +		return NULL;
> > +
> > +	/* only support singleton container with nesting type */
> > +	list_for_each_entry(d, &iommu->domain_list, next) {
> > +		list_for_each_entry(g, &d->group_list, next) {
> > +			if (!group) {
> > +				group = g;
> > +				break;
> > +			}
> 
> 
> We break out of the inner loop only to pointlessly continue in the outer loop
> when we could simply return g and remove the second group pointer altogether
> (use "group" instead of "g" if so).

how about below? :-)

	/* only support singleton container with nesting type */
	list_for_each_entry(d, &iommu->domain_list, next) {
		list_for_each_entry(group, &d->group_list, next) {
			break;
		}
	}

> 
> > +		}
> > +	}
> > +	return group;
> > +}
> > +
> >  static int put_pfn(unsigned long pfn, int prot);
> >
> >  static struct vfio_group *vfio_iommu_find_iommu_group(struct
> > vfio_iommu *iommu, @@ -2351,6 +2378,48 @@ static int
> vfio_iommu_resv_refresh(struct vfio_iommu *iommu,
> >  	return ret;
> >  }
> >
> > +static int vfio_dev_bind_gpasid_fn(struct device *dev, void *data) {
> > +	struct domain_capsule *dc = (struct domain_capsule *)data;
> > +	unsigned long arg = *(unsigned long *) dc->data;
> > +
> > +	return iommu_sva_bind_gpasid(dc->domain, dev, (void __user *) arg);
> > +}
> > +
> > +static int vfio_dev_unbind_gpasid_fn(struct device *dev, void *data)
> > +{
> > +	struct domain_capsule *dc = (struct domain_capsule *)data;
> > +	unsigned long arg = *(unsigned long *) dc->data;
> > +
> > +	iommu_sva_unbind_gpasid(dc->domain, dev, (void __user *) arg);
> > +	return 0;
> > +}
> > +
> > +static int __vfio_dev_unbind_gpasid_fn(struct device *dev, void
> > +*data) {
> > +	struct domain_capsule *dc = (struct domain_capsule *)data;
> > +	struct iommu_gpasid_bind_data *unbind_data =
> > +				(struct iommu_gpasid_bind_data *) dc->data;
> > +
> > +	__iommu_sva_unbind_gpasid(dc->domain, dev, unbind_data);
> > +	return 0;
> > +}
> > +
> > +static void vfio_group_unbind_gpasid_fn(ioasid_t pasid, void *data) {
> > +	struct domain_capsule *dc = (struct domain_capsule *) data;
> > +	struct iommu_gpasid_bind_data unbind_data;
> > +
> > +	unbind_data.argsz = offsetof(struct iommu_gpasid_bind_data, vendor);
> > +	unbind_data.flags = 0;
> > +	unbind_data.hpasid = pasid;
> > +
> > +	dc->data = &unbind_data;
> > +
> > +	iommu_group_for_each_dev(dc->group->iommu_group,
> > +				 dc, __vfio_dev_unbind_gpasid_fn); }
> > +
> >  static void vfio_iommu_type1_detach_group(void *iommu_data,
> >  					  struct iommu_group *iommu_group)
> { @@ -2394,6 +2463,21 @@
> > static void vfio_iommu_type1_detach_group(void *iommu_data,
> >  		if (!group)
> >  			continue;
> >
> > +		if (iommu->nesting_info && iommu->vmm &&
> > +		    (iommu->nesting_info->features &
> > +					IOMMU_NESTING_FEAT_BIND_PGTBL)) {
> > +			struct domain_capsule dc = { .group = group,
> > +						     .domain = domain->domain,
> > +						     .data = NULL };
> > +
> > +			/*
> > +			 * Unbind page tables bound with system wide PASIDs
> > +			 * which are allocated to user space.
> > +			 */
> > +			vfio_mm_for_each_pasid(iommu->vmm, &dc,
> > +					       vfio_group_unbind_gpasid_fn);
> > +		}
> > +
> >  		vfio_iommu_detach_group(domain, group);
> >  		update_dirty_scope = !group->pinned_page_dirty_scope;
> >  		list_del(&group->next);
> > @@ -2942,6 +3026,89 @@ static int vfio_iommu_type1_pasid_request(struct
> vfio_iommu *iommu,
> >  	}
> >  }
> >
> > +static long vfio_iommu_handle_pgtbl_op(struct vfio_iommu *iommu,
> > +				       bool is_bind, unsigned long arg) {
> > +	struct iommu_nesting_info *info;
> > +	struct domain_capsule dc = { .data = &arg };
> > +	struct vfio_group *group;
> > +	struct vfio_domain *domain;
> > +	int ret;
> > +
> > +	mutex_lock(&iommu->lock);
> > +
> > +	info = iommu->nesting_info;
> > +	if (!info || !(info->features & IOMMU_NESTING_FEAT_BIND_PGTBL)) {
> > +		ret = -ENOTSUPP;
> > +		goto out_unlock_iommu;
> > +	}
> > +
> > +	if (!iommu->vmm) {
> > +		ret = -EINVAL;
> > +		goto out_unlock_iommu;
> > +	}
> > +
> > +	group = vfio_find_nesting_group(iommu);
> > +	if (!group) {
> > +		ret = -EINVAL;
> > +		goto out_unlock_iommu;
> > +	}
> > +
> > +	domain = list_first_entry(&iommu->domain_list,
> > +				      struct vfio_domain, next);
> > +	dc.group = group;
> > +	dc.domain = domain->domain;
> > +
> > +	/* Avoid race with other containers within the same process */
> > +	vfio_mm_pasid_lock(iommu->vmm);
> > +
> > +	if (is_bind) {
> > +		ret = iommu_group_for_each_dev(group->iommu_group, &dc,
> > +					       vfio_dev_bind_gpasid_fn);
> > +		if (ret)
> > +			iommu_group_for_each_dev(group->iommu_group,
> &dc,
> > +						 vfio_dev_unbind_gpasid_fn);
> > +	} else {
> > +		iommu_group_for_each_dev(group->iommu_group,
> > +					 &dc, vfio_dev_unbind_gpasid_fn);
> > +		ret = 0;
> > +	}
> > +
> > +	vfio_mm_pasid_unlock(iommu->vmm);
> > +out_unlock_iommu:
> > +	mutex_unlock(&iommu->lock);
> > +	return ret;
> > +}
> > +
> > +static long vfio_iommu_type1_nesting_op(struct vfio_iommu *iommu,
> > +					unsigned long arg)
> > +{
> > +	struct vfio_iommu_type1_nesting_op hdr;
> > +	unsigned int minsz;
> > +	int ret;
> > +
> > +	minsz = offsetofend(struct vfio_iommu_type1_nesting_op, flags);
> > +
> > +	if (copy_from_user(&hdr, (void __user *)arg, minsz))
> > +		return -EFAULT;
> > +
> > +	if (hdr.argsz < minsz || hdr.flags & ~VFIO_NESTING_OP_MASK)
> > +		return -EINVAL;
> > +
> > +	switch (hdr.flags & VFIO_NESTING_OP_MASK) {
> > +	case VFIO_IOMMU_NESTING_OP_BIND_PGTBL:
> > +		ret = vfio_iommu_handle_pgtbl_op(iommu, true, arg + minsz);
> > +		break;
> > +	case VFIO_IOMMU_NESTING_OP_UNBIND_PGTBL:
> > +		ret = vfio_iommu_handle_pgtbl_op(iommu, false, arg + minsz);
> > +		break;
> > +	default:
> > +		ret = -EINVAL;
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> >  static long vfio_iommu_type1_ioctl(void *iommu_data,
> >  				   unsigned int cmd, unsigned long arg)  { @@ -
> 2960,6 +3127,8 @@
> > static long vfio_iommu_type1_ioctl(void *iommu_data,
> >  		return vfio_iommu_type1_dirty_pages(iommu, arg);
> >  	case VFIO_IOMMU_PASID_REQUEST:
> >  		return vfio_iommu_type1_pasid_request(iommu, arg);
> > +	case VFIO_IOMMU_NESTING_OP:
> > +		return vfio_iommu_type1_nesting_op(iommu, arg);
> >  	}
> >
> >  	return -ENOTTY;
> > diff --git a/drivers/vfio/vfio_pasid.c b/drivers/vfio/vfio_pasid.c
> > index 2ea9f1a..20f1e72 100644
> > --- a/drivers/vfio/vfio_pasid.c
> > +++ b/drivers/vfio/vfio_pasid.c
> > @@ -30,6 +30,7 @@ struct vfio_mm {
> >  	struct kref		kref;
> >  	struct vfio_mm_token	token;
> >  	int			ioasid_sid;
> > +	struct mutex		pasid_lock;
> 
> 
> Introducing holes in the data structure again, mind the alignment.
> This wastes 8 byte.  Thanks,

sure. also it's likely to remove @pasid_quota. so it should avoid the
hole as well.

Regards,
Yi Liu

> Alex
> 
> 
> >  	int			pasid_quota;
> >  	struct list_head	next;
> >  };
> > @@ -97,6 +98,7 @@ struct vfio_mm *vfio_mm_get_from_task(struct
> task_struct *task)
> >  	kref_init(&vmm->kref);
> >  	vmm->token.val = (unsigned long long) mm;
> >  	vmm->pasid_quota = pasid_quota;
> > +	mutex_init(&vmm->pasid_lock);
> >
> >  	list_add(&vmm->next, &vfio_pasid.vfio_mm_list);
> >  out:
> > @@ -134,12 +136,40 @@ void vfio_pasid_free_range(struct vfio_mm *vmm,
> >  	 * IOASID core will notify PASID users (e.g. IOMMU driver) to
> >  	 * teardown necessary structures depending on the to-be-freed
> >  	 * PASID.
> > +	 * Hold pasid_lock to avoid race with PASID usages like bind/
> > +	 * unbind page tables to requested PASID.
> >  	 */
> > +	mutex_lock(&vmm->pasid_lock);
> >  	for (; pasid <= max; pasid++)
> >  		ioasid_free(pasid);
> > +	mutex_unlock(&vmm->pasid_lock);
> >  }
> >  EXPORT_SYMBOL_GPL(vfio_pasid_free_range);
> >
> > +int vfio_mm_for_each_pasid(struct vfio_mm *vmm, void *data,
> > +			   void (*fn)(ioasid_t id, void *data)) {
> > +	int ret;
> > +
> > +	mutex_lock(&vmm->pasid_lock);
> > +	ret = ioasid_set_for_each_ioasid(vmm->ioasid_sid, fn, data);
> > +	mutex_unlock(&vmm->pasid_lock);
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(vfio_mm_for_each_pasid);
> > +
> > +void vfio_mm_pasid_lock(struct vfio_mm *vmm) {
> > +	mutex_lock(&vmm->pasid_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(vfio_mm_pasid_lock);
> > +
> > +void vfio_mm_pasid_unlock(struct vfio_mm *vmm) {
> > +	mutex_unlock(&vmm->pasid_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(vfio_mm_pasid_unlock);
> > +
> >  static int __init vfio_pasid_init(void)  {
> >  	mutex_init(&vfio_pasid.vfio_mm_lock);
> > diff --git a/include/linux/vfio.h b/include/linux/vfio.h index
> > 8e60a32..9028a09 100644
> > --- a/include/linux/vfio.h
> > +++ b/include/linux/vfio.h
> > @@ -105,6 +105,11 @@ int vfio_mm_ioasid_sid(struct vfio_mm *vmm);
> > extern int vfio_pasid_alloc(struct vfio_mm *vmm, int min, int max);
> > extern void vfio_pasid_free_range(struct vfio_mm *vmm,
> >  					ioasid_t min, ioasid_t max);
> > +extern int vfio_mm_for_each_pasid(struct vfio_mm *vmm, void *data,
> > +				  void (*fn)(ioasid_t id, void *data)); extern void
> > +vfio_mm_pasid_lock(struct vfio_mm *vmm); extern void
> > +vfio_mm_pasid_unlock(struct vfio_mm *vmm);
> > +
> >  #else
> >  static inline struct vfio_mm *vfio_mm_get_from_task(struct
> > task_struct *task)  { @@ -129,6 +134,21 @@ static inline void
> > vfio_pasid_free_range(struct vfio_mm *vmm,
> >  					  ioasid_t min, ioasid_t max)
> >  {
> >  }
> > +
> > +static inline int vfio_mm_for_each_pasid(struct vfio_mm *vmm, void *data,
> > +					 void (*fn)(ioasid_t id, void *data)) {
> > +	return -ENOTTY;
> > +}
> > +
> > +static inline void vfio_mm_pasid_lock(struct vfio_mm *vmm) { }
> > +
> > +static inline void vfio_mm_pasid_unlock(struct vfio_mm *vmm) { }
> > +
> >  #endif /* CONFIG_VFIO_PASID */
> >
> >  /*
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 657b2db..2c9def8 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -1198,6 +1198,36 @@ struct vfio_iommu_type1_pasid_request {
> >
> >  #define VFIO_IOMMU_PASID_REQUEST	_IO(VFIO_TYPE, VFIO_BASE + 18)
> >
> > +/**
> > + * VFIO_IOMMU_NESTING_OP - _IOW(VFIO_TYPE, VFIO_BASE + 19,
> > + *				struct vfio_iommu_type1_nesting_op)
> > + *
> > + * This interface allows user space to utilize the nesting IOMMU
> > + * capabilities as reported through VFIO_IOMMU_GET_INFO.
> > + *
> > + * @data[] types defined for each op:
> > + *
> +=================+===========================================
> ====+
> > + * | NESTING OP      |                  @data[]                      |
> > + *
> +=================+===========================================
> ====+
> > + * | BIND_PGTBL      |      struct iommu_gpasid_bind_data            |
> > + * +-----------------+-----------------------------------------------+
> > + * | UNBIND_PGTBL    |      struct iommu_gpasid_bind_data            |
> > + *
> > ++-----------------+-----------------------------------------------+
> > + *
> > + * returns: 0 on success, -errno on failure.
> > + */
> > +struct vfio_iommu_type1_nesting_op {
> > +	__u32	argsz;
> > +	__u32	flags;
> > +#define VFIO_NESTING_OP_MASK	(0xffff) /* lower 16-bits for op */
> > +	__u8	data[];
> > +};
> > +
> > +#define VFIO_IOMMU_NESTING_OP_BIND_PGTBL	(0)
> > +#define VFIO_IOMMU_NESTING_OP_UNBIND_PGTBL	(1)
> > +
> > +#define VFIO_IOMMU_NESTING_OP		_IO(VFIO_TYPE,
> VFIO_BASE + 19)
> > +
> >  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU
> > -------- */
> >
> >  /*

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