Hi Pierre, On 30/11/17 12:34, Pierre Morel wrote: > When userland VFIO defines a new IOMMU for a guest it may > want to specify to the guest the physical limits of > the underlying host IOMMU to avoid access to forbidden > memory ranges. > > Currently, the vfio_iommu_type1 driver does not report this > information to userland. > > Let's extend the vfio_iommu_type1_info structure reported > by the ioctl VFIO_IOMMU_GET_INFO command to report the > IOMMU limits as new uint64_t entries aperture_start and > aperture_end. > > Let's also extend the flags bit map to add a flag specifying > if this extension of the info structure is reported or not. > > Signed-off-by: Pierre Morel <[email protected]> > --- > drivers/vfio/vfio_iommu_type1.c | 42 > +++++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/vfio.h | 3 +++ > 2 files changed, 45 insertions(+) > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 8549cb1..7da5fe0 100644 > --- a/drivers/vfio/vfio_iommu_type1.c > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -1526,6 +1526,40 @@ static int vfio_domains_have_iommu_cache(struct > vfio_iommu *iommu) > return ret; > } > > +/** > + * vfio_get_aperture - report minimal aperture of a vfio_iommu > + * @iommu: the current vfio_iommu > + * @start: a pointer to the aperture start > + * @end : a pointer to the aperture end > + * > + * This function iterate on the domains using the given vfio_iommu > + * and restrict the aperture to the minimal aperture common > + * to all domains sharing this vfio_iommu. > + */ > +static void vfio_get_aperture(struct vfio_iommu *iommu, uint64_t *start, > + uint64_t *end) > +{ > + struct iommu_domain_geometry geometry; > + struct vfio_domain *domain; > + > + *start = 0; > + *end = U64_MAX; > + > + mutex_lock(&iommu->lock); > + /* loop on all domains using this vfio_iommu */ > + list_for_each_entry(domain, &iommu->domain_list, next) { > + iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY, > + &geometry); > + if (geometry.force_aperture) { > + if (geometry.aperture_start > *start) > + *start = geometry.aperture_start; > + if (geometry.aperture_end < *end) > + *end = geometry.aperture_end; > + } > + } > + mutex_unlock(&iommu->lock); > +} > + > static long vfio_iommu_type1_ioctl(void *iommu_data, > unsigned int cmd, unsigned long arg) > { > @@ -1560,6 +1594,14 @@ static long vfio_iommu_type1_ioctl(void *iommu_data, > > info.iova_pgsizes = vfio_pgsize_bitmap(iommu); > > + minsz = min_t(size_t, info.argsz, sizeof(info)); > + if (minsz >= offsetofend(struct vfio_iommu_type1_info, > + aperture_end)) { > + info.flags |= VFIO_IOMMU_INFO_APERTURE; > + vfio_get_aperture(iommu, &info.aperture_start, > + &info.aperture_end); > + } > + > return copy_to_user((void __user *)arg, &info, minsz) ? > -EFAULT : 0; > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > index 0fb25fb..780d909 100644 > --- a/include/uapi/linux/vfio.h > +++ b/include/uapi/linux/vfio.h > @@ -519,6 +519,9 @@ struct vfio_iommu_type1_info { > __u32 flags; > #define VFIO_IOMMU_INFO_PGSIZES (1 << 0) /* supported page sizes info */ > __u64 iova_pgsizes; /* Bitmap of supported page sizes */ > +#define VFIO_IOMMU_INFO_APERTURE (1 << 1) /* supported aperture info */ > + __u64 aperture_start; /* start of DMA aperture */ > + __u64 aperture_end; /* end of DMA aperture */ > }; > > #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12) >
In the past I was told by Alex that using the capability chain extensions to add some new capabilities was a better approach: https://lkml.org/lkml/2016/4/6/751 I did that kind of exercise in [PATCH v9 7/7] vfio/type1: return MSI geometry through VFIO_IOMMU_GET_INFO capability chains https://lists.linuxfoundation.org/pipermail/iommu/2016-May/016892.html The patch was not used eventually but maybe that can help. Thanks Eric
