Hi Eric, > From: Auger Eric <eric.auger@xxxxxxxxxx> > 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@xxxxxxxxxx> > >> 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@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> > >>> --- > >>> 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 | 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 > >
