Date:   Mon, 20 Jul 2020 08:51:24 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Auger Eric <eric.auger@...hat.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "joro@...tes.org" <joro@...tes.org>
CC:     "Tian, Kevin" <kevin.tian@...el.com>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Tian, Jun J" <jun.j.tian@...el.com>,
        "Sun, Yi Y" <yi.y.sun@...el.com>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "Wu, Hao" <hao.wu@...el.com>,
        "stefanha@...il.com" <stefanha@...il.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v5 04/15] vfio/type1: Report iommu nesting info to
 userspace

Hi Eric,

> From: Auger Eric <eric.auger@...hat.com>
> Sent: Monday, July 20, 2020 4:33 PM
> 
> Yi,
> 
> On 7/20/20 9:51 AM, Liu, Yi L wrote:
> > Hi Eric,
> >
> >> From: Auger Eric <eric.auger@...hat.com>
> >> Sent: Saturday, July 18, 2020 1:34 AM
> >>
> >> Yi,
> >>
> >> On 7/12/20 1:20 PM, Liu Yi L wrote:
> >>> This patch exports iommu nesting capability info to user space
> >>> through VFIO. User space is expected to check this info for supported uAPIs (e.g.
> >> it is not only to check the supported uAPIS but rather to know which
> >> callbacks it must call upon vIOMMU events and which features are
> >> supported by the physical IOMMU.
> >
> > yes, will refine the description per your comment.
> >
> >>> PASID alloc/free, bind page table, and cache invalidation) and the
> >>> vendor specific format information for first level/stage page table
> >>> that will be bound to.
> >>>
> >>> The nesting info is available only after the nesting iommu type is
> >>> set for a container.
> >> to NESTED type
> >
> > you mean "The nesting info is available only after container set to be NESTED
> type."
> >
> > right?
> correct

got you.

> >
> >>  Current implementation imposes one limitation - one
> >>> nesting container should include at most one group. The philosophy
> >>> of vfio container is having all groups/devices within the container
> >>> share the same IOMMU context. When vSVA is enabled, one IOMMU
> >>> context could include one 2nd-level address space and multiple 1st-level address
> spaces.
> >>> While the 2nd-level address space is reasonably sharable by multiple
> >>> groups , blindly sharing 1st-level address spaces across all groups
> >>> within the container might instead break the guest expectation. In
> >>> the future sub/ super container concept might be introduced to allow
> >>> partial address space sharing within an IOMMU context. But for now
> >>> let's go with this restriction by requiring singleton container for
> >>> using nesting iommu features. Below link has the related discussion about this
> decision.
> >>
> >> Maybe add a note about SMMU related changes spotted by Jean.
> >
> > I guess you mean the comments Jean gave in patch 3/15, right? I'll
> > copy his comments and also give the below link as well.
> >
> > https://lore.kernel.org/kvm/20200717090900.GC4850@myrica/
> correct

I see.

Regards,
Yi Liu

> Thanks
> 
> Eric
> >
> >>>
> >>> https://lkml.org/lkml/2020/5/15/1028
> >>>
> >>> Cc: Kevin Tian <kevin.tian@...el.com>
> >>> CC: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> >>> Cc: Alex Williamson <alex.williamson@...hat.com>
> >>> Cc: Eric Auger <eric.auger@...hat.com>
> >>> Cc: Jean-Philippe Brucker <jean-philippe@...aro.org>
> >>> Cc: Joerg Roedel <joro@...tes.org>
> >>> Cc: Lu Baolu <baolu.lu@...ux.intel.com>
> >>> Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
> >>> ---
> >>> v4 -> v5:
> >>> *) address comments from Eric Auger.
> >>> *) return struct iommu_nesting_info for
> >> VFIO_IOMMU_TYPE1_INFO_CAP_NESTING as
> >>>    cap is much "cheap", if needs extension in future, just define another cap.
> >>>    https://lore.kernel.org/kvm/20200708132947.5b7ee954@x1.home/
> >>>
> >>> v3 -> v4:
> >>> *) address comments against v3.
> >>>
> >>> v1 -> v2:
> >>> *) added in v2
> >>> ---
> >>>  drivers/vfio/vfio_iommu_type1.c | 102
> >> +++++++++++++++++++++++++++++++++++-----
> >>>  include/uapi/linux/vfio.h       |  19 ++++++++
> >>>  2 files changed, 109 insertions(+), 12 deletions(-)
> >>>
> >>> diff --git a/drivers/vfio/vfio_iommu_type1.c
> >>> b/drivers/vfio/vfio_iommu_type1.c index 3bd70ff..ed80104 100644
> >>> --- a/drivers/vfio/vfio_iommu_type1.c
> >>> +++ b/drivers/vfio/vfio_iommu_type1.c
> >>> @@ -62,18 +62,20 @@ MODULE_PARM_DESC(dma_entry_limit,
> >>>  		 "Maximum number of user DMA mappings per container (65535).");
> >>>
> >>>  struct vfio_iommu {
> >>> -	struct list_head	domain_list;
> >>> -	struct list_head	iova_list;
> >>> -	struct vfio_domain	*external_domain; /* domain for external user */
> >>> -	struct mutex		lock;
> >>> -	struct rb_root		dma_list;
> >>> -	struct blocking_notifier_head notifier;
> >>> -	unsigned int		dma_avail;
> >>> -	uint64_t		pgsize_bitmap;
> >>> -	bool			v2;
> >>> -	bool			nesting;
> >>> -	bool			dirty_page_tracking;
> >>> -	bool			pinned_page_dirty_scope;
> >>> +	struct list_head		domain_list;
> >>> +	struct list_head		iova_list;
> >>> +	/* domain for external user */
> >>> +	struct vfio_domain		*external_domain;
> >>> +	struct mutex			lock;
> >>> +	struct rb_root			dma_list;
> >>> +	struct blocking_notifier_head	notifier;
> >>> +	unsigned int			dma_avail;
> >>> +	uint64_t			pgsize_bitmap;
> >>> +	bool				v2;
> >>> +	bool				nesting;
> >>> +	bool				dirty_page_tracking;
> >>> +	bool				pinned_page_dirty_scope;
> >>> +	struct iommu_nesting_info	*nesting_info;
> >>>  };
> >>>
> >>>  struct vfio_domain {
> >>> @@ -130,6 +132,9 @@ struct vfio_regions {
> >>>  #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)	\
> >>>  					(!list_empty(&iommu->domain_list))
> >>>
> >>> +#define CONTAINER_HAS_DOMAIN(iommu)	(((iommu)-
> >external_domain) || \
> >>> +					 (!list_empty(&(iommu)->domain_list)))
> >>> +
> >>>  #define DIRTY_BITMAP_BYTES(n)	(ALIGN(n, BITS_PER_TYPE(u64)) /
> >> BITS_PER_BYTE)
> >>>
> >>>  /*
> >>> @@ -1929,6 +1934,13 @@ static void
> >>> vfio_iommu_iova_insert_copy(struct
> >> vfio_iommu *iommu,
> >>>
> >>>  	list_splice_tail(iova_copy, iova);  }
> >>> +
> >>> +static void vfio_iommu_release_nesting_info(struct vfio_iommu
> >>> +*iommu) {
> >>> +	kfree(iommu->nesting_info);
> >>> +	iommu->nesting_info = NULL;
> >>> +}
> >>> +
> >>>  static int vfio_iommu_type1_attach_group(void *iommu_data,
> >>>  					 struct iommu_group *iommu_group)
> { @@ -1959,6 +1971,12 @@
> >>> static int vfio_iommu_type1_attach_group(void
> >> *iommu_data,
> >>>  		}
> >>>  	}
> >>>
> >>> +	/* Nesting type container can include only one group */
> >>> +	if (iommu->nesting && CONTAINER_HAS_DOMAIN(iommu)) {
> >>> +		mutex_unlock(&iommu->lock);
> >>> +		return -EINVAL;
> >>> +	}
> >>> +
> >>>  	group = kzalloc(sizeof(*group), GFP_KERNEL);
> >>>  	domain = kzalloc(sizeof(*domain), GFP_KERNEL);
> >>>  	if (!group || !domain) {
> >>> @@ -2029,6 +2047,32 @@ static int vfio_iommu_type1_attach_group(void
> >> *iommu_data,
> >>>  	if (ret)
> >>>  		goto out_domain;
> >>>
> >>> +	/* Nesting cap info is available only after attaching */
> >>> +	if (iommu->nesting) {
> >>> +		struct iommu_nesting_info tmp = { .size = 0, };
> >>> +
> >>> +		/* First get the size of vendor specific nesting info */
> >>> +		ret = iommu_domain_get_attr(domain->domain,
> >>> +					    DOMAIN_ATTR_NESTING,
> >>> +					    &tmp);
> >>> +		if (ret)
> >>> +			goto out_detach;
> >>> +
> >>> +		iommu->nesting_info = kzalloc(tmp.size, GFP_KERNEL);
> >>> +		if (!iommu->nesting_info) {
> >>> +			ret = -ENOMEM;
> >>> +			goto out_detach;
> >>> +		}
> >>> +
> >>> +		/* Now get the nesting info */
> >>> +		iommu->nesting_info->size = tmp.size;
> >>> +		ret = iommu_domain_get_attr(domain->domain,
> >>> +					    DOMAIN_ATTR_NESTING,
> >>> +					    iommu->nesting_info);
> >>> +		if (ret)
> >>> +			goto out_detach;
> >
> > get nesting_info failure will result in group_attach failure.[1]
> >
> >>> +	}
> >>> +
> >>>  	/* Get aperture info */
> >>>  	iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY,
> >> &geo);
> >>>
> >>> @@ -2138,6 +2182,7 @@ static int vfio_iommu_type1_attach_group(void
> >> *iommu_data,
> >>>  	return 0;
> >>>
> >>>  out_detach:
> >>> +	vfio_iommu_release_nesting_info(iommu);
> >>>  	vfio_iommu_detach_group(domain, group);
> >>>  out_domain:
> >>>  	iommu_domain_free(domain->domain);
> >>> @@ -2338,6 +2383,8 @@ static void vfio_iommu_type1_detach_group(void
> >> *iommu_data,
> >>>  					vfio_iommu_unmap_unpin_all(iommu);
> >>>  				else
> >>>
> >> 	vfio_iommu_unmap_unpin_reaccount(iommu);
> >>> +
> >>> +				vfio_iommu_release_nesting_info(iommu);
> >>>  			}
> >>>  			iommu_domain_free(domain->domain);
> >>>  			list_del(&domain->next);
> >>> @@ -2546,6 +2593,31 @@ static int
> >>> vfio_iommu_migration_build_caps(struct
> >> vfio_iommu *iommu,
> >>>  	return vfio_info_add_capability(caps, &cap_mig.header,
> >>> sizeof(cap_mig));  }
> >>>
> >>> +static int vfio_iommu_info_add_nesting_cap(struct vfio_iommu *iommu,
> >>> +					   struct vfio_info_cap *caps) {
> >>> +	struct vfio_info_cap_header *header;
> >>> +	struct vfio_iommu_type1_info_cap_nesting *nesting_cap;
> >>> +	size_t size;
> >>> +
> >>> +	size = offsetof(struct vfio_iommu_type1_info_cap_nesting, info) +
> >>> +		iommu->nesting_info->size;
> >>> +
> >>> +	header = vfio_info_cap_add(caps, size,
> >>> +				   VFIO_IOMMU_TYPE1_INFO_CAP_NESTING, 1);
> >>> +	if (IS_ERR(header))
> >>> +		return PTR_ERR(header);
> >>> +
> >>> +	nesting_cap = container_of(header,
> >>> +				   struct vfio_iommu_type1_info_cap_nesting,
> >>> +				   header);
> >>> +
> >>> +	memcpy(&nesting_cap->info, iommu->nesting_info,
> >>> +	       iommu->nesting_info->size);
> >> you must check whether nesting_info is non NULL before doing that.
> >
> > it's now validated in the caller of this function. :-)
> ah ok sorry I missed that.
> >
> >> Besides I agree with Jean on the fact it may be better to not report
> >> the capability if nested is not supported.
> >
> > I see. in this patch, just few lines below [2], vfio only reports
> > nesting cap when iommu->nesting_info is non-null. so even if userspace
> > selected nesting type, it may fail at the VFIO_SET_IOMMU phase since
> > group_attach will be failed for NESTED type container if host iommu
> > doesn’t support nesting. the code is marked as [1] in this email.
> OK that's already there then.
>
> Thanks
> 
> Eric
> >
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>>  static int vfio_iommu_type1_get_info(struct vfio_iommu *iommu,
> >>>  				     unsigned long arg)
> >>>  {
> >>> @@ -2581,6 +2653,12 @@ static int vfio_iommu_type1_get_info(struct
> >> vfio_iommu *iommu,
> >>>  	if (!ret)
> >>>  		ret = vfio_iommu_iova_build_caps(iommu, &caps);
> >>>
> >>> +	if (iommu->nesting_info) {
> >>> +		ret = vfio_iommu_info_add_nesting_cap(iommu, &caps);
> >>> +		if (ret)
> >>> +			return ret;
> >
> > here checks nesting_info before reporting nesting cap. [2]
> >
> >>> +	}
> >>> +
> >>>  	mutex_unlock(&iommu->lock);
> >>>
> >>>  	if (ret)
> >>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> >>> index 9204705..46a78af 100644
> >>> --- a/include/uapi/linux/vfio.h
> >>> +++ b/include/uapi/linux/vfio.h
> >>> @@ -14,6 +14,7 @@
> >>>
> >>>  #include <linux/types.h>
> >>>  #include <linux/ioctl.h>
> >>> +#include <linux/iommu.h>
> >>>
> >>>  #define VFIO_API_VERSION	0
> >>>
> >>> @@ -1039,6 +1040,24 @@ struct vfio_iommu_type1_info_cap_migration {
> >>>  	__u64	max_dirty_bitmap_size;		/* in bytes */
> >>>  };
> >>>
> >>> +/*
> >>> + * The nesting capability allows to report the related capability
> >>> + * and info for nesting iommu type.
> >>> + *
> >>> + * The structures below define version 1 of this capability.
> >>> + *
> >>> + * User space selected VFIO_TYPE1_NESTING_IOMMU type should check
> >>> + * this capto get supported features.
> >> s/capto/capability to get
> >
> > got it.
> >
> > Regards,
> > Yi Liu
> >
> >>> + *
> >>> + * @info: the nesting info provided by IOMMU driver.
> >>> + */
> >>> +#define VFIO_IOMMU_TYPE1_INFO_CAP_NESTING  3
> >>> +
> >>> +struct vfio_iommu_type1_info_cap_nesting {
> >>> +	struct	vfio_info_cap_header header;
> >>> +	struct iommu_nesting_info info;
> >>> +};
> >>> +
> >>>  #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
> >>>
> >>>  /**
> >>>
> >>
> >> Thanks
> >>
> >> Eric
> >

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