On Thu, 10 Sep 2020 03:45:20 -0700 Liu Yi L <yi.l.liu@xxxxxxxxx> wrote: > This patch exports iommu nesting capability info to user space through > VFIO. Userspace 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 container set to be NESTED type. > Current implementation imposes one limitation - one nesting container > should include at most one iommu 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. > > https://lore.kernel.org/kvm/20200515115924.37e6996d@xxxxxxxxx/ > > This patch also changes the NESTING type container behaviour. Something > that would have succeeded before will now fail: Before this series, if > user asked for a VFIO_IOMMU_TYPE1_NESTING, it would have succeeded even > if the SMMU didn't support stage-2, as the driver would have silently > fallen back on stage-1 mappings (which work exactly the same as stage-2 > only since there was no nesting supported). After the series, we do check > for DOMAIN_ATTR_NESTING so if user asks for VFIO_IOMMU_TYPE1_NESTING and > the SMMU doesn't support stage-2, the ioctl fails. But it should be a good > fix and completely harmless. Detail can be found in below link as well. > > https://lore.kernel.org/kvm/20200717090900.GC4850@myrica/ > > 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> > --- > v6 -> v7: > *) using vfio_info_add_capability() for adding nesting cap per suggestion > from Eric. > > v5 -> v6: > *) address comments against v5 from Eric Auger. > *) don't report nesting cap to userspace if the nesting_info->format is > invalid. > > 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@xxxxxxx/ > > v3 -> v4: > *) address comments against v3. > > v1 -> v2: > *) added in v2 > --- > drivers/vfio/vfio_iommu_type1.c | 92 +++++++++++++++++++++++++++++++++++------ > include/uapi/linux/vfio.h | 19 +++++++++ > 2 files changed, 99 insertions(+), 12 deletions(-) > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index c992973..3c0048b 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; Nit, not as important as the previous alignment, but might as well move this up with the uint64_t pgsize_bitmap with the bools at the end of the structure to avoid adding new gaps. > }; > > 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) > > /* > @@ -1992,6 +1997,13 @@ 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) > { > @@ -2022,6 +2034,12 @@ 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) { > @@ -2092,6 +2110,25 @@ 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) { > + int size = sizeof(struct iommu_nesting_info); > + > + iommu->nesting_info = kzalloc(size, GFP_KERNEL); > + if (!iommu->nesting_info) { > + ret = -ENOMEM; > + goto out_detach; > + } > + > + /* Now get the nesting info */ > + iommu->nesting_info->argsz = size; > + ret = iommu_domain_get_attr(domain->domain, > + DOMAIN_ATTR_NESTING, > + iommu->nesting_info); > + if (ret) > + goto out_detach; > + } > + > /* Get aperture info */ > iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY, &geo); > > @@ -2201,6 +2238,7 @@ 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); > @@ -2401,6 +2439,8 @@ 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); > @@ -2609,6 +2649,32 @@ 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_add_nesting_cap(struct vfio_iommu *iommu, > + struct vfio_info_cap *caps) > +{ > + struct vfio_iommu_type1_info_cap_nesting nesting_cap; > + size_t size; > + > + /* when nesting_info is null, no need to go further */ > + if (!iommu->nesting_info) > + return 0; > + > + /* when @format of nesting_info is 0, fail the call */ > + if (iommu->nesting_info->format == 0) > + return -ENOENT; Should we fail this in the attach_group? Seems the user would be in a bad situation here if they successfully created a nesting container but can't get info. Is there backwards compatibility we're trying to maintain with this? > + > + size = offsetof(struct vfio_iommu_type1_info_cap_nesting, info) + > + iommu->nesting_info->argsz; > + > + nesting_cap.header.id = VFIO_IOMMU_TYPE1_INFO_CAP_NESTING; > + nesting_cap.header.version = 1; > + > + memcpy(&nesting_cap.info, iommu->nesting_info, > + iommu->nesting_info->argsz); > + > + return vfio_info_add_capability(caps, &nesting_cap.header, size); > +} > + > static int vfio_iommu_type1_get_info(struct vfio_iommu *iommu, > unsigned long arg) > { > @@ -2644,6 +2710,8 @@ static int vfio_iommu_type1_get_info(struct vfio_iommu *iommu, > if (!ret) > ret = vfio_iommu_iova_build_caps(iommu, &caps); > > + ret = vfio_iommu_add_nesting_cap(iommu, &caps); Why don't we follow either the naming scheme or the error handling scheme of the previous caps? Seems like this should be: if (!ret) ret = vfio_iommu_nesting_build_caps(...); Thanks, Alex > + > mutex_unlock(&iommu->lock); > > if (ret) > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > index 9204705..ff40f9e 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. > + * > + * Nested capabilities should be checked by the userspace after > + * setting VFIO_TYPE1_NESTING_IOMMU. > + * > + * @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) > > /**
