RE: [PATCH v4 07/15] vfio/type1: Add VFIO_IOMMU_PASID_REQUEST (alloc/free)

From: Liu, Yi L
Date: Tue Jul 07 2020 - 05:51:31 EST

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Hi Eric,

> From: Auger Eric <eric.auger@xxxxxxxxxx>
> Sent: Monday, July 6, 2020 11:18 PM
>
> Hi Yi,
>
> On 7/4/20 1:26 PM, Liu Yi L wrote:
> > This patch allows user space 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@xxxxxxxxx>
> > CC: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > Cc: Eric Auger <eric.auger@xxxxxxxxxx>
> > Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> > Cc: Joerg Roedel <joro@xxxxxxxxxx>
> > Cc: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> > Signed-off-by: Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > ---
> > 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?"
> >
> > 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 | 84
> +++++++++++++++++++++++++++++++++++++++++
> > drivers/vfio/vfio_pasid.c | 10 +++++
> > include/linux/vfio.h | 6 +++
> > include/uapi/linux/vfio.h | 36 ++++++++++++++++++
> > 5 files changed, 137 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 80623b8..29726ca 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;
> > }
> > @@ -2075,6 +2081,25 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
> > goto out_detach;
> > }
> > iommu->nesting_info = info;
> > +
> > + if (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 */
> > @@ -2860,6 +2885,63 @@ static int vfio_iommu_type1_dirty_pages(struct
> vfio_iommu *iommu,
> > return -EINVAL;
> > }
> >
> > +static int vfio_iommu_type1_pasid_alloc(struct vfio_iommu *iommu,
> > + unsigned int min,
> > + unsigned int max)
> > +{
> > + int ret = -EOPNOTSUPP;
> > +
> > + mutex_lock(&iommu->lock);
> > + if (iommu->vmm)
> > + ret = vfio_pasid_alloc(iommu->vmm, min, max);
> > + mutex_unlock(&iommu->lock);
> > + return ret;
> > +}
> > +
> > +static int vfio_iommu_type1_pasid_free(struct vfio_iommu *iommu,
> > + unsigned int min,
> > + unsigned int max)
> > +{
> > + int ret = -EOPNOTSUPP;
> > +
> > + mutex_lock(&iommu->lock);
> > + if (iommu->vmm) {
> > + vfio_pasid_free_range(iommu->vmm, min, max);
> > + ret = 0;
> > + }
> > + mutex_unlock(&iommu->lock);
> > + return ret;
> > +}
> > +
> > +static int vfio_iommu_type1_pasid_request(struct vfio_iommu *iommu,
> > + unsigned long arg)
> > +{
> > + struct vfio_iommu_type1_pasid_request req;
> > + unsigned long minsz;
> > +
> > + 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;
> > +
> > + switch (req.flags & VFIO_PASID_REQUEST_MASK) {
> > + case VFIO_IOMMU_FLAG_ALLOC_PASID:
> > + return vfio_iommu_type1_pasid_alloc(iommu,
> > + req.range.min, req.range.max);
> > + case VFIO_IOMMU_FLAG_FREE_PASID:
> > + return vfio_iommu_type1_pasid_free(iommu,
> > + req.range.min, req.range.max);
> > + default:
> > + return -EINVAL;
> > + }
> > +}
> > +
> > static long vfio_iommu_type1_ioctl(void *iommu_data,
> > unsigned int cmd, unsigned long arg)
> > {
> > @@ -2876,6 +2958,8 @@ 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);
> > }
> >
> > return -ENOTTY;
> > diff --git a/drivers/vfio/vfio_pasid.c b/drivers/vfio/vfio_pasid.c
> > index c46b870..6f907db 100644
> > --- a/drivers/vfio/vfio_pasid.c
> > +++ b/drivers/vfio/vfio_pasid.c
> > @@ -53,6 +53,7 @@ void vfio_mm_put(struct vfio_mm *vmm)
> > {
> > kref_put_mutex(&vmm->kref, vfio_mm_release,
> &vfio_pasid.vfio_mm_lock);
> > }
> > +EXPORT_SYMBOL_GPL(vfio_mm_put);
> I think this should be belong to [5/15]

yeah, the implementation is in [5/15], but the user is in this patch, so export
it in this patch.

> >
> > static void vfio_mm_get(struct vfio_mm *vmm)
> > {
> > @@ -104,6 +105,13 @@ struct vfio_mm *vfio_mm_get_from_task(struct
> task_struct *task)
> > mmput(mm);
> > return vmm;
> > }
> > +EXPORT_SYMBOL_GPL(vfio_mm_get_from_task);
> same

the same with above.

> > +
> > +int vfio_mm_ioasid_sid(struct vfio_mm *vmm)
> extern?
> same

why need extern? as it's used in this patch, so add it in this patch.

> > +{
> > + return vmm->ioasid_sid;
> > +}
> > +EXPORT_SYMBOL_GPL(vfio_mm_ioasid_sid);
> >
> > int vfio_pasid_alloc(struct vfio_mm *vmm, int min, int max)
> > {
> > @@ -113,6 +121,7 @@ int vfio_pasid_alloc(struct vfio_mm *vmm, int min, int max)
> >
> > return (pasid == INVALID_IOASID) ? -ENOSPC : pasid;
> > }
> > +EXPORT_SYMBOL_GPL(vfio_pasid_alloc);
> same

same as above reason. :-)

> >
> > void vfio_pasid_free_range(struct vfio_mm *vmm,
> > ioasid_t min, ioasid_t max)
> > @@ -130,6 +139,7 @@ void vfio_pasid_free_range(struct vfio_mm *vmm,
> > for (; pasid <= max; pasid++)
> > ioasid_free(pasid);
> > }
> > +EXPORT_SYMBOL_GPL(vfio_pasid_free_range);
> same

same as above.

> >
> > static int __init vfio_pasid_init(void)
> > {
> > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> > index 9da6468..35c922a 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);
> > +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 3e3de9c..fe267b8e 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -1169,6 +1169,42 @@ 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 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 through VFIO_IOMMU_GET_INFO.
> name the capability?

yep. will add it.

Regards,
Yi Liu

> > + *
> > + * @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 -------- */
> >
> > /*
> >
>
> Thanks
>
> Eric

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