RE: [PATCH v5 04/15] vfio/type1: Report iommu nesting info to userspace

Liu, Yi L
2020-07-20T08:51:34Z

Hi Eric,

> From: Auger Eric <eric.auger@redhat.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@redhat.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@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: Liu Yi L <yi.l.liu@intel.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
> >