On Wed, 24 Jun 2020 01:55:16 -0700 Liu Yi L <yi.l.liu@xxxxxxxxx> 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. > 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. 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-leve 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. > > https://lkml.org/lkml/2020/5/15/1028 > > Cc: Kevin Tian <kevin.tian@xxxxxxxxx> > CC: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx> > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx> > Cc: Eric Auger <eric.auger@xxxxxxxxxx> > Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> > Cc: Joerg Roedel <joro@xxxxxxxxxx> > Cc: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx> > --- > drivers/vfio/vfio_iommu_type1.c | 73 +++++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/vfio.h | 9 +++++ > 2 files changed, 82 insertions(+) > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 7accb59..8c143d5 100644 > --- a/drivers/vfio/vfio_iommu_type1.c > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -72,6 +72,7 @@ struct vfio_iommu { > uint64_t pgsize_bitmap; > bool v2; > bool nesting; > + struct iommu_nesting_info *nesting_info; > bool dirty_page_tracking; > bool pinned_page_dirty_scope; > }; Mind the structure packing and alignment, placing a pointer in the middle of a section of bools is going to create wasteful holes in the data structure. > @@ -130,6 +131,9 @@ struct vfio_regions { > #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \ > (!list_empty(&iommu->domain_list)) > > +#define IS_DOMAIN_IN_CONTAINER(iommu) ((iommu->external_domain) || \ > + (!list_empty(&iommu->domain_list))) > + > #define DIRTY_BITMAP_BYTES(n) (ALIGN(n, BITS_PER_TYPE(u64)) / BITS_PER_BYTE) > > /* > @@ -1959,6 +1963,12 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, > } > } > > + /* Nesting type container can include only one group */ > + if (iommu->nesting && IS_DOMAIN_IN_CONTAINER(iommu)) { > + mutex_unlock(&iommu->lock); > + return -EINVAL; > + } > + > group = kzalloc(sizeof(*group), GFP_KERNEL); > domain = kzalloc(sizeof(*domain), GFP_KERNEL); > if (!group || !domain) { > @@ -2029,6 +2039,36 @@ 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; > + struct iommu_nesting_info *info; > + > + /* 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; > + > + info = kzalloc(tmp.size, GFP_KERNEL); > + if (!info) { > + ret = -ENOMEM; > + goto out_detach; > + } > + > + /* Now get the nesting info */ > + info->size = tmp.size; > + ret = iommu_domain_get_attr(domain->domain, > + DOMAIN_ATTR_NESTING, > + info); > + if (ret) { > + kfree(info); > + goto out_detach; > + } > + iommu->nesting_info = info; > + } > + > /* Get aperture info */ > iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY, &geo); > > @@ -2138,6 +2178,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, > return 0; > > out_detach: > + kfree(iommu->nesting_info); This looks prone to a use-after-free. > vfio_iommu_detach_group(domain, group); > out_domain: > iommu_domain_free(domain->domain); > @@ -2338,6 +2379,8 @@ static void vfio_iommu_type1_detach_group(void *iommu_data, > vfio_iommu_unmap_unpin_all(iommu); > else > vfio_iommu_unmap_unpin_reaccount(iommu); > + > + kfree(iommu->nesting_info); As does this. Set to NULL since get_info tests the pointer before trying to use it. > } > iommu_domain_free(domain->domain); > list_del(&domain->next); > @@ -2546,6 +2589,30 @@ 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 = sizeof(*nesting_cap) + 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); > + > + return 0; > +} > + > static int vfio_iommu_type1_get_info(struct vfio_iommu *iommu, > unsigned long arg) > { > @@ -2586,6 +2653,12 @@ static int vfio_iommu_type1_get_info(struct vfio_iommu *iommu, > if (ret) > return ret; > > + if (iommu->nesting_info) { > + ret = vfio_iommu_info_add_nesting_cap(iommu, &caps); > + if (ret) > + return ret; > + } > + > if (caps.size) { > info.flags |= VFIO_IOMMU_INFO_CAPS; > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > index eca66926..f1f39e1 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> Why? We're not directly referencing any IOMMU UAPI structures here. > > #define VFIO_API_VERSION 0 > > @@ -1039,6 +1040,14 @@ struct vfio_iommu_type1_info_cap_migration { > __u64 max_dirty_bitmap_size; /* in bytes */ > }; > > +#define VFIO_IOMMU_TYPE1_INFO_CAP_NESTING 3 > + > +struct vfio_iommu_type1_info_cap_nesting { > + struct vfio_info_cap_header header; > + __u32 flags; I think there's an alignment issue here for a uapi. The header field is 8-bytes total and info[] should start at an 8-byte alignment to allow data[] within info to have 8-byte alignment. This could lead to the structure having a compiler dependent size and offsets. We should add a 4-byte reserved field here to resolve. > + __u8 info[]; > +}; This should have a lot more description around it, a user could not infer that info[] is including a struct iommu_nesting_info from the information provided here. Thanks, Alex > + > #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12) > > /**
