RE: [PATCH v6 07/15] vfio/type1: Add VFIO_IOMMU_PASID_REQUEST (alloc/free)

Liu, Yi L
2020-08-17T05:29:45Z

Thanks, Eric.

Regards,
Yi Liu

> From: Auger Eric <eric.auger@redhat.com>
> Sent: Sunday, August 16, 2020 12:30 AM
>
> Yi,
>
> On 7/28/20 8:27 AM, Liu Yi L wrote:
> > This patch allows userspace to request PASID allocation/free, e.g.
> > when serving the request from the guest.
> >
> > PASIDs that are not freed by userspace are automatically freed when
> > the IOASID set is destroyed when process exits.
> >
> > 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>
> > Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> > v5 -> v6:
> > *) address comments from Eric against v5. remove the alloc/free helper.
> >
> > v4 -> v5:
> > *) address comments from Eric Auger.
> > *) the comments for the PASID_FREE request is addressed in patch 5/15 of
> > this series.
> >
> > v3 -> v4:
> > *) address comments from v3, except the below comment against the range
> > of PASID_FREE request. needs more help on it.
> > "> +if (req.range.min > req.range.max)
> >
> > Is it exploitable that a user can spin the kernel for a long time in
> > the case of a free by calling this with [0, MAX_UINT] regardless of
> > their actual allocations?"
> >
> > https://lore.kernel.org/linux-iommu/20200702151832.048b44d1@x1.home/
> >
> > v1 -> v2:
> > *) move the vfio_mm related code to be a seprate module
> > *) use a single structure for alloc/free, could support a range of
> > PASIDs
> > *) fetch vfio_mm at group_attach time instead of at iommu driver open
> > time
> > ---
> > drivers/vfio/Kconfig | 1 +
> > drivers/vfio/vfio_iommu_type1.c | 69
> +++++++++++++++++++++++++++++++++++++++++
> > drivers/vfio/vfio_pasid.c | 10 ++++++
> > include/linux/vfio.h | 6 ++++
> > include/uapi/linux/vfio.h | 37 ++++++++++++++++++++++
> > 5 files changed, 123 insertions(+)
> >
> > diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig index
> > 3d8a108..95d90c6 100644
> > --- a/drivers/vfio/Kconfig
> > +++ b/drivers/vfio/Kconfig
> > @@ -2,6 +2,7 @@
> > config VFIO_IOMMU_TYPE1
> > tristate
> > depends on VFIO
> > + select VFIO_PASID if (X86)
> > default n
> >
> > config VFIO_IOMMU_SPAPR_TCE
> > diff --git a/drivers/vfio/vfio_iommu_type1.c
> > b/drivers/vfio/vfio_iommu_type1.c index 18ff0c3..ea89c7c 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c
> > @@ -76,6 +76,7 @@ struct vfio_iommu {
> > bool dirty_page_tracking;
> > bool pinned_page_dirty_scope;
> > struct iommu_nesting_info *nesting_info;
> > + struct vfio_mm *vmm;
> > };
> >
> > struct vfio_domain {
> > @@ -1937,6 +1938,11 @@ static void vfio_iommu_iova_insert_copy(struct
> > vfio_iommu *iommu,
> >
> > static void vfio_iommu_release_nesting_info(struct vfio_iommu *iommu)
> > {
> > + if (iommu->vmm) {
> > + vfio_mm_put(iommu->vmm);
> > + iommu->vmm = NULL;
> > + }
> > +
> > kfree(iommu->nesting_info);
> > iommu->nesting_info = NULL;
> > }
> > @@ -2071,6 +2077,26 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
> > iommu->nesting_info);
> > if (ret)
> > goto out_detach;
> > +
> > + if (iommu->nesting_info->features &
> > + IOMMU_NESTING_FEAT_SYSWIDE_PASID)
> {
> > + struct vfio_mm *vmm;
> > + int sid;
> > +
> > + vmm = vfio_mm_get_from_task(current);
> > + if (IS_ERR(vmm)) {
> > + ret = PTR_ERR(vmm);
> > + goto out_detach;
> > + }
> > + iommu->vmm = vmm;
> > +
> > + sid = vfio_mm_ioasid_sid(vmm);
> > + ret = iommu_domain_set_attr(domain->domain,
> > + DOMAIN_ATTR_IOASID_SID,
> > + &sid);
> > + if (ret)
> > + goto out_detach;
> > + }
> > }
> >
> > /* Get aperture info */
> > @@ -2859,6 +2885,47 @@ static int vfio_iommu_type1_dirty_pages(struct
> vfio_iommu *iommu,
> > return -EINVAL;
> > }
> >
> > +static int vfio_iommu_type1_pasid_request(struct vfio_iommu *iommu,
> > + unsigned long arg)
> > +{
> > + struct vfio_iommu_type1_pasid_request req;
> > + unsigned long minsz;
> > + int ret;
> > +
> > + minsz = offsetofend(struct vfio_iommu_type1_pasid_request, range);
> > +
> > + if (copy_from_user(&req, (void __user *)arg, minsz))
> > + return -EFAULT;
> > +
> > + if (req.argsz < minsz || (req.flags & ~VFIO_PASID_REQUEST_MASK))
> > + return -EINVAL;
> > +
> > + if (req.range.min > req.range.max)
> > + return -EINVAL;
> > +
> > + mutex_lock(&iommu->lock);
> > + if (!iommu->vmm) {
> > + mutex_unlock(&iommu->lock);
> > + return -EOPNOTSUPP;
> > + }
> > +
> > + switch (req.flags & VFIO_PASID_REQUEST_MASK) {
> > + case VFIO_IOMMU_FLAG_ALLOC_PASID:
> > + ret = vfio_pasid_alloc(iommu->vmm, req.range.min,
> > + req.range.max);
> > + break;
> > + case VFIO_IOMMU_FLAG_FREE_PASID:
> > + vfio_pasid_free_range(iommu->vmm, req.range.min,
> > + req.range.max);
> > + ret = 0;
> > + break;
> > + default:
> > + ret = -EINVAL;
> > + }
> > + mutex_unlock(&iommu->lock);
> > + return ret;
> > +}
> > +
> > static long vfio_iommu_type1_ioctl(void *iommu_data,
> > unsigned int cmd, unsigned long arg) { @@ -
> 2875,6 +2942,8 @@
> > static long vfio_iommu_type1_ioctl(void *iommu_data,
> > return vfio_iommu_type1_unmap_dma(iommu, arg);
> > case VFIO_IOMMU_DIRTY_PAGES:
> > return vfio_iommu_type1_dirty_pages(iommu, arg);
> > + case VFIO_IOMMU_PASID_REQUEST:
> > + return vfio_iommu_type1_pasid_request(iommu, arg);
> > default:
> > return -ENOTTY;
> > }
> > diff --git a/drivers/vfio/vfio_pasid.c b/drivers/vfio/vfio_pasid.c
> > index befcf29..8d0317f 100644
> > --- a/drivers/vfio/vfio_pasid.c
> > +++ b/drivers/vfio/vfio_pasid.c
> > @@ -61,6 +61,7 @@ void vfio_mm_put(struct vfio_mm *vmm) {
> > kref_put_mutex(&vmm->kref, vfio_mm_release, &vfio_mm_lock); }
> > +EXPORT_SYMBOL_GPL(vfio_mm_put);
> >
> > static void vfio_mm_get(struct vfio_mm *vmm)
> > {
> > @@ -114,6 +115,13 @@ struct vfio_mm *vfio_mm_get_from_task(struct
> task_struct *task)
> > mmput(mm);
> > return vmm;
> > }
> > +EXPORT_SYMBOL_GPL(vfio_mm_get_from_task);
> > +
> > +int vfio_mm_ioasid_sid(struct vfio_mm *vmm)
> > +{
> > + return vmm->ioasid_sid;
> > +}
> > +EXPORT_SYMBOL_GPL(vfio_mm_ioasid_sid);
> >
> > /*
> > * Find PASID within @min and @max
> > @@ -202,6 +210,7 @@ int vfio_pasid_alloc(struct vfio_mm *vmm, int min, int max)
> >
> > return pasid;
> > }
> > +EXPORT_SYMBOL_GPL(vfio_pasid_alloc);
> >
> > void vfio_pasid_free_range(struct vfio_mm *vmm,
> > ioasid_t min, ioasid_t max)
> > @@ -218,6 +227,7 @@ void vfio_pasid_free_range(struct vfio_mm *vmm,
> > vfio_remove_pasid(vmm, vid);
> > mutex_unlock(&vmm->pasid_lock);
> > }
> > +EXPORT_SYMBOL_GPL(vfio_pasid_free_range);
> >
> > static int __init vfio_pasid_init(void)
> > {
> > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> > index 31472a9..a355d01 100644
> > --- a/include/linux/vfio.h
> > +++ b/include/linux/vfio.h
> > @@ -101,6 +101,7 @@ struct vfio_mm;
> > #if IS_ENABLED(CONFIG_VFIO_PASID)
> > extern struct vfio_mm *vfio_mm_get_from_task(struct task_struct *task);
> > extern void vfio_mm_put(struct vfio_mm *vmm);
> > +extern int vfio_mm_ioasid_sid(struct vfio_mm *vmm);
> > extern int vfio_pasid_alloc(struct vfio_mm *vmm, int min, int max);
> > extern void vfio_pasid_free_range(struct vfio_mm *vmm,
> > ioasid_t min, ioasid_t max);
> > @@ -114,6 +115,11 @@ static inline void vfio_mm_put(struct vfio_mm *vmm)
> > {
> > }
> >
> > +static inline int vfio_mm_ioasid_sid(struct vfio_mm *vmm)
> > +{
> > + return -ENOTTY;
> > +}
> > +
> > static inline int vfio_pasid_alloc(struct vfio_mm *vmm, int min, int max)
> > {
> > return -ENOTTY;
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 0cf3d6d..6d79557 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -1172,6 +1172,43 @@ struct vfio_iommu_type1_dirty_bitmap_get {
> >
> > #define VFIO_IOMMU_DIRTY_PAGES _IO(VFIO_TYPE, VFIO_BASE + 17)
> >
> > +/**
> > + * VFIO_IOMMU_PASID_REQUEST - _IOWR(VFIO_TYPE, VFIO_BASE + 18,
> > + * struct vfio_iommu_type1_pasid_request)
> > + *
> > + * PASID (Processor Address Space ID) is a PCIe concept for tagging
> > + * address spaces in DMA requests. When system-wide PASID allocation
> > + * is required by the underlying iommu driver (e.g. Intel VT-d), this
> > + * provides an interface for userspace to request pasid alloc/free
> > + * for its assigned devices. Userspace should check the availability
> > + * of this API by checking VFIO_IOMMU_TYPE1_INFO_CAP_NESTING through
> > + * VFIO_IOMMU_GET_INFO.
> > + *
> > + * @flags=VFIO_IOMMU_FLAG_ALLOC_PASID, allocate a single PASID within
> @range.
> > + * @flags=VFIO_IOMMU_FLAG_FREE_PASID, free the PASIDs within @range.
> > + * @range is [min, max], which means both @min and @max are inclusive.
> > + * ALLOC_PASID and FREE_PASID are mutually exclusive.
> > + *
> > + * returns: allocated PASID value on success, -errno on failure for
> > + * ALLOC_PASID;
> > + * 0 for FREE_PASID operation;
> > + */
> > +struct vfio_iommu_type1_pasid_request {
> > + __u32 argsz;
> > +#define VFIO_IOMMU_FLAG_ALLOC_PASID (1 << 0)
> > +#define VFIO_IOMMU_FLAG_FREE_PASID (1 << 1)
> > + __u32 flags;
> > + struct {
> > + __u32 min;
> > + __u32 max;
> > + } range;
> > +};
> > +
> > +#define VFIO_PASID_REQUEST_MASK (VFIO_IOMMU_FLAG_ALLOC_PASID | \
> > + VFIO_IOMMU_FLAG_FREE_PASID)
> > +
> > +#define VFIO_IOMMU_PASID_REQUEST _IO(VFIO_TYPE, VFIO_BASE + 18)
> > +
> > /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
> >
> > /*
> >
> Looks OK to me
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
>
>
> Thanks
>
> Eric