From: Alex Williamson <alex.williamson@redhat.com>
To: Liu Yi L <yi.l.liu@intel.com>
Cc: eric.auger@redhat.com, baolu.lu@linux.intel.com, joro@8bytes.org,
kevin.tian@intel.com, jacob.jun.pan@linux.intel.com,
ashok.raj@intel.com, jun.j.tian@intel.com, yi.y.sun@intel.com,
jean-philippe@linaro.org, peterx@redhat.com, hao.wu@intel.com,
iommu@lists.linux-foundation.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 03/14] vfio/type1: Report iommu nesting info to userspace
Date: Thu, 2 Jul 2020 12:38:47 -0600 [thread overview]
Message-ID: <20200702123847.384e7460@x1.home> (raw)
In-Reply-To: <1592988927-48009-4-git-send-email-yi.l.liu@intel.com>
On Wed, 24 Jun 2020 01:55:16 -0700
Liu Yi L <yi.l.liu@intel.com> 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@intel.com>
> CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Lu Baolu <baolu.lu@linux.intel.com>
> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> ---
> 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)
>
> /**
next prev parent reply other threads:[~2020-07-02 18:39 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 8:55 [PATCH v3 00/14] vfio: expose virtual Shared Virtual Addressing to VMs Liu Yi L
2020-06-24 8:55 ` [PATCH v3 01/14] vfio/type1: Refactor vfio_iommu_type1_ioctl() Liu Yi L
2020-07-02 21:21 ` Alex Williamson
2020-07-03 3:46 ` Liu, Yi L
2020-06-24 8:55 ` [PATCH v3 02/14] iommu: Report domain nesting info Liu Yi L
2020-06-26 7:47 ` Jean-Philippe Brucker
2020-06-26 16:04 ` Robin Murphy
2020-06-27 6:53 ` Liu, Yi L
2020-06-30 1:20 ` Tian, Kevin
2020-06-27 6:14 ` Liu, Yi L
2020-06-29 9:24 ` Stefan Hajnoczi
2020-06-29 12:23 ` Liu, Yi L
2020-06-30 2:00 ` Tian, Kevin
2020-06-30 3:45 ` Liu, Yi L
2020-07-03 9:59 ` Stefan Hajnoczi
2020-07-02 17:54 ` Alex Williamson
2020-07-03 3:53 ` Liu, Yi L
2020-06-24 8:55 ` [PATCH v3 03/14] vfio/type1: Report iommu nesting info to userspace Liu Yi L
2020-07-02 18:38 ` Alex Williamson [this message]
2020-07-03 6:05 ` Liu, Yi L
2020-07-03 13:03 ` Liu, Yi L
2020-06-24 8:55 ` [PATCH v3 04/14] vfio: Add PASID allocation/free support Liu Yi L
2020-07-02 21:17 ` Alex Williamson
2020-07-03 6:08 ` Liu, Yi L
2020-06-24 8:55 ` [PATCH v3 05/14] iommu/vt-d: Support setting ioasid set to domain Liu Yi L
2020-06-24 8:55 ` [PATCH v3 06/14] vfio/type1: Add VFIO_IOMMU_PASID_REQUEST (alloc/free) Liu Yi L
2020-07-02 21:18 ` Alex Williamson
2020-07-03 6:28 ` Liu, Yi L
2020-07-08 8:16 ` Liu, Yi L
2020-07-08 19:54 ` Alex Williamson
2020-07-09 0:32 ` Liu, Yi L
2020-07-09 1:56 ` Tian, Kevin
2020-07-09 2:08 ` Liu, Yi L
2020-07-09 2:18 ` Tian, Kevin
2020-07-09 2:26 ` Liu, Yi L
2020-07-09 7:16 ` Liu, Yi L
2020-07-09 14:27 ` Alex Williamson
2020-07-09 18:05 ` Jacob Pan
2020-07-10 5:39 ` Liu, Yi L
2020-07-10 12:55 ` Alex Williamson
2020-07-10 13:03 ` Liu, Yi L
2020-06-24 8:55 ` [PATCH v3 07/14] iommu: Pass domain to sva_unbind_gpasid() Liu Yi L
2020-06-24 8:55 ` [PATCH v3 08/14] iommu/vt-d: Check ownership for PASIDs from user-space Liu Yi L
2020-06-24 8:55 ` [PATCH v3 09/14] vfio/type1: Support binding guest page tables to PASID Liu Yi L
2020-07-02 21:19 ` Alex Williamson
2020-07-03 6:46 ` Liu, Yi L
2020-06-24 8:55 ` [PATCH v3 10/14] vfio/type1: Allow invalidating first-level/stage IOMMU cache Liu Yi L
2020-07-02 21:19 ` Alex Williamson
2020-07-03 3:47 ` Liu, Yi L
2020-06-24 8:55 ` [PATCH v3 11/14] vfio/type1: Add vSVA support for IOMMU-backed mdevs Liu Yi L
2020-06-24 8:55 ` [PATCH v3 12/14] vfio/pci: Expose PCIe PASID capability to guest Liu Yi L
2020-06-24 8:55 ` [PATCH v3 13/14] vfio: Document dual stage control Liu Yi L
2020-06-29 9:21 ` Stefan Hajnoczi
2020-06-29 9:24 ` Liu, Yi L
2020-06-24 8:55 ` [PATCH v3 14/14] iommu/vt-d: Support reporting nesting capability info Liu Yi L
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