Hi Yi, On 4/1/20 2:51 PM, Liu, Yi L wrote: > Hi Eric, > >> From: Auger Eric <eric.au...@redhat.com> >> Sent: Wednesday, April 1, 2020 4:51 PM >> To: Liu, Yi L <yi.l....@intel.com>; alex.william...@redhat.com >> Subject: Re: [PATCH v1 5/8] vfio/type1: Report 1st-level/stage-1 format to >> userspace >> >> Hi Yi, >> On 3/22/20 1:32 PM, Liu, Yi L wrote: >>> From: Liu Yi L <yi.l....@intel.com> >>> >>> VFIO exposes IOMMU nesting translation (a.k.a dual stage translation) >>> capability to userspace. Thus applications like QEMU could support >>> vIOMMU with hardware's nesting translation capability for pass-through >>> devices. Before setting up nesting translation for pass-through devices, >>> QEMU and other applications need to learn the supported 1st-lvl/stage-1 >>> translation structure format like page table format. >>> >>> Take vSVA (virtual Shared Virtual Addressing) as an example, to support >>> vSVA for pass-through devices, QEMU setup nesting translation for pass- >>> through devices. The guest page table are configured to host as 1st-lvl/ >>> stage-1 page table. Therefore, guest format should be compatible with >>> host side. >>> >>> This patch reports the supported 1st-lvl/stage-1 page table format on the >>> current platform to userspace. QEMU and other alike applications should >>> use this format info when trying to setup IOMMU nesting translation on >>> host IOMMU. >>> >>> Cc: Kevin Tian <kevin.t...@intel.com> >>> CC: Jacob Pan <jacob.jun....@linux.intel.com> >>> Cc: Alex Williamson <alex.william...@redhat.com> >>> Cc: Eric Auger <eric.au...@redhat.com> >>> Cc: Jean-Philippe Brucker <jean-phili...@linaro.org> >>> Signed-off-by: Liu Yi L <yi.l....@intel.com> >>> --- >>> drivers/vfio/vfio_iommu_type1.c | 56 >> +++++++++++++++++++++++++++++++++++++++++ >>> include/uapi/linux/vfio.h | 1 + >>> 2 files changed, 57 insertions(+) >>> >>> diff --git a/drivers/vfio/vfio_iommu_type1.c >>> b/drivers/vfio/vfio_iommu_type1.c >>> index 9aa2a67..82a9e0b 100644 >>> --- a/drivers/vfio/vfio_iommu_type1.c >>> +++ b/drivers/vfio/vfio_iommu_type1.c >>> @@ -2234,11 +2234,66 @@ static int vfio_iommu_type1_pasid_free(struct >> vfio_iommu *iommu, >>> return ret; >>> } >>> >>> +static int vfio_iommu_get_stage1_format(struct vfio_iommu *iommu, >>> + u32 *stage1_format) >> vfio_pasid_format() to be homogeneous with vfio_pgsize_bitmap() which >> does the same kind of enumeration of the vfio_iommu domains > > yes, similar. > >>> +{ >>> + struct vfio_domain *domain; >>> + u32 format = 0, tmp_format = 0; >>> + int ret; >> ret = -EINVAL; > > got it. > >>> + >>> + mutex_lock(&iommu->lock); >>> + if (list_empty(&iommu->domain_list)) { >> goto out_unlock; > > right. >>> + mutex_unlock(&iommu->lock); >>> + return -EINVAL; >>> + } >>> + >>> + list_for_each_entry(domain, &iommu->domain_list, next) { >>> + if (iommu_domain_get_attr(domain->domain, >>> + DOMAIN_ATTR_PASID_FORMAT, &format)) { >> I can find DOMAIN_ATTR_PASID_FORMAT in Jacob's v9 but not in v10 > > oops, I guess he somehow missed. you may find it in below link. > > https://github.com/luxis1999/linux-vsva/commit/bf14b11a12f74d58ad3ee626a5d891de395082eb > >>> + ret = -EINVAL; >> could be removed > > sure. > >>> + format = 0; >>> + goto out_unlock; >>> + } >>> + /* >>> + * format is always non-zero (the first format is >>> + * IOMMU_PASID_FORMAT_INTEL_VTD which is 1). For >>> + * the reason of potential different backed IOMMU >>> + * formats, here we expect to have identical formats >>> + * in the domain list, no mixed formats support. >>> + * return -EINVAL to fail the attempt of setup >>> + * VFIO_TYPE1_NESTING_IOMMU if non-identical formats >>> + * are detected. >>> + */ >>> + if (tmp_format && tmp_format != format) { >>> + ret = -EINVAL; >> could be removed > > got it. > >>> + format = 0; >>> + goto out_unlock; >>> + } >>> + >>> + tmp_format = format; >>> + } >>> + ret = 0; >>> + >>> +out_unlock: >>> + if (format) >> if (!ret) ? then you can remove the format = 0 in case of error. > > oh, yes. > >>> + *stage1_format = format; >>> + mutex_unlock(&iommu->lock); >>> + return ret; >>> +} >>> + >>> 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; >>> + u32 formats = 0; >>> + int ret; >>> + >>> + ret = vfio_iommu_get_stage1_format(iommu, &formats); >>> + if (ret) { >>> + pr_warn("Failed to get stage-1 format\n"); >> trace triggered by userspace to be removed? > > sure. > >>> + return ret; >>> + } >>> >>> header = vfio_info_cap_add(caps, sizeof(*nesting_cap), >>> VFIO_IOMMU_TYPE1_INFO_CAP_NESTING, 1); >>> @@ -2254,6 +2309,7 @@ static int vfio_iommu_info_add_nesting_cap(struct >> vfio_iommu *iommu, >>> /* nesting iommu type supports PASID requests (alloc/free) */ >>> nesting_cap->nesting_capabilities |= VFIO_IOMMU_PASID_REQS; >> What is the meaning for ARM? > > I think it's just a software capability exposed to userspace, on > userspace side, it has a choice to use it or not. :-) The reason > define it and report it in cap nesting is that I'd like to make > the pasid alloc/free be available just for IOMMU with type > VFIO_IOMMU_TYPE1_NESTING. Please feel free tell me if it is not > good for ARM. We can find a proper way to report the availability.
Well it is more a question for jean-Philippe. Do we have a system wide PASID allocation on ARM? Thanks Eric > >>> } >>> + nesting_cap->stage1_formats = formats; >> as spotted by Kevin, since a single format is supported, rename > > ok, I was believing it may be possible on ARM or so. :-) will > rename it. > > I'll refine the patch per your above comments. > > Regards, > Yi Liu > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu