Hi Alex,
> From: Alex Williamson < alex.william...@redhat.com >
> Sent: Friday, July 3, 2020 2:39 AM
>
> On Wed, 24 Jun 2020 01:55:16 -0700
> Liu Yi L <yi.l....@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.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>
> > Cc: Joerg Roedel <j...@8bytes.org>
> > Cc: Lu Baolu <baolu...@linux.intel.com>
> > Signed-off-by: Liu Yi L <yi.l....@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.
how about below? Add the @nesting_info and @vmm in the end of this struct.
I've two questions, the first one is how the place the comment of the
@external_domain; second question is do you want me to move the @nesting
field to be near-by with the @nesting_info and @vmm. :) please let me know
your preference.
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 iommu_nesting_info *nesting_info;
struct vfio_mm *vmm;
};
> > @@ -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.
how about setting iommu->nesting_info to NULL? just as the next comment
from you.
> > 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.
got 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.
oh, yes. will remove it.
> >
> > #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.
got it. or how about defining the flags as __u64?
>
> > + __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,
sure. BTW. do you think it is necessary to add a flag to indicate the info[]
is a struct iommu_nesting_info? or as a start, it's not necessary to do it.
Regards,
Yi Liu
> Alex
>
> > +
> > #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
> >
> > /**
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