Hi Eric, > From: Auger Eric < eric.auger@xxxxxxxxxx > > Sent: Monday, July 6, 2020 9:45 PM > > Hi Yi, > > On 7/6/20 3:10 PM, Liu, Yi L wrote: > > Hi Eric, > > > >> From: Auger Eric <eric.auger@xxxxxxxxxx> > >> Sent: Monday, July 6, 2020 6:37 PM > >> > >> Yi, > >> > >> On 7/4/20 1:26 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. > >>> 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 > >> level > > > > oh, yes. > > > >>> , 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> > >>> --- > >>> v3 -> v4: > >>> *) address comments against v3. > >>> > >>> v1 -> v2: > >>> *) added in v2 > >>> --- > >>> > >>> drivers/vfio/vfio_iommu_type1.c | 105 > >> +++++++++++++++++++++++++++++++++++----- > >>> include/uapi/linux/vfio.h | 16 ++++++ > >>> 2 files changed, 109 insertions(+), 12 deletions(-) > >>> > >>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >>> index 7accb59..80623b8 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; > >>> + struct vfio_domain *external_domain; /* domain for > >>> + external user */ > >> nit: put the comment before the field? > > > > do you mean below? > > > > + /* domain for external user */ > > + struct vfio_domain *external_domain; > yes that's what I meant got you. :-) > > > >>> + 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 IS_DOMAIN_IN_CONTAINER(iommu) ((iommu- > >external_domain) || \ > >>> + (!list_empty(&iommu->domain_list))) > >> rename into something like CONTAINER_HAS_DOMAIN()? > > > > got it. > > > >>> + > >>> #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 && 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 +2047,36 @@ 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); > >> nit: you may directly use iommu->nesting_info > > > > got you. > > > >>> + 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); > >> ... and set it back to NULL here if it fails > > > > and maybe no need to free it here as vfio_iommu_release_nesting_info() > > will free the nesting_info. > > > >>> + goto out_detach; > >>> + } > >>> + iommu->nesting_info = info; > >>> + } > >>> + > >>> /* Get aperture info */ > >>> iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY, > >> &geo); > >>> > >>> @@ -2138,6 +2186,7 @@ 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 +2387,8 @@ 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 +2597,30 @@ 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 +2661,12 @@ 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 9204705..3e3de9c 100644 > >>> --- a/include/uapi/linux/vfio.h > >>> +++ b/include/uapi/linux/vfio.h > >>> @@ -1039,6 +1039,22 @@ struct vfio_iommu_type1_info_cap_migration { > >>> __u64 max_dirty_bitmap_size; /* in bytes */ > >>> }; > >>> > >>> +#define VFIO_IOMMU_TYPE1_INFO_CAP_NESTING 3 > >> > >> You may improve the documentation by taking examples from the above caps. > > > > yes, it is. I somehow broke the style. how about below? > > > > > > > > /* > > * 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 should check this cap for setup nesting iommu type. > before setting up stage 1 information? The wording above sounds a bit > confusing to me as it can be interpreted as before choosing > VFIO_TYPE1_NESTING_IOMMU. > oh, yep. this cap is available only for nesting type iommu. a.ka. VFIO_TYPE1_NESTING_IOMMU is selected. > You also need to document it returns the capability only after a group > is attached - which looks strange by the way -. I think this should be aligned with VFIO_IOMMU_GET_INFO usage. GET_INFO is meaningful after VFIO_SET_IOMMU, which includes group attaching. Regards, Yi Liu > Thanks > > Eric > > * > > * @info: the nesting info provided by IOMMU driver. Today > > * it is expected to be a struct iommu_nesting_info > > * data. > > #define VFIO_IOMMU_TYPE1_INFO_CAP_NESTING 3 > > > > struct vfio_iommu_type1_info_cap_nesting { > > ... > > }; > > > >>> + > >>> +/* > >>> + * Reporting nesting info to user space. > >>> + * > >>> + * @info: the nesting info provided by IOMMU driver. Today > >>> + * it is expected to be a struct iommu_nesting_info > >>> + * data. > >> Is it expected to change? > > > > honestly, I'm not quite sure on it. I did considered to embed > > struct iommu_nesting_info here instead of using info[]. but I > > hesitated as using info[] may leave more flexibility on this > > struct. how about your opinion? perhaps it's fine to embed the > > struct iommu_nesting_info here as long as VFIO is setup nesting > > based on IOMMU UAPI. > > > >>> + */ > >>> +struct vfio_iommu_type1_info_cap_nesting { > >>> + struct vfio_info_cap_header header; > >>> + __u32 flags; > >> You may document flags. > > > > sure. it's reserved for future. > > > > Regards, > > Yi Liu > > > >>> + __u32 padding; > >>> + __u8 info[]; > >>> +}; > >>> + > >>> #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12) > >>> > >>> /** > >>> > >> Thanks > >> > >> Eric > >
