Hi Alex,
> From: Alex Williamson <[email protected]>
> Sent: Saturday, September 12, 2020 5:38 AM
>
> On Thu, 10 Sep 2020 03:45:24 -0700
> Liu Yi L <[email protected]> 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 <[email protected]>
> > CC: Jacob Pan <[email protected]>
> > Cc: Alex Williamson <[email protected]>
> > Cc: Eric Auger <[email protected]>
> > Cc: Jean-Philippe Brucker <[email protected]>
> > Cc: Joerg Roedel <[email protected]>
> > Cc: Lu Baolu <[email protected]>
> > Signed-off-by: Liu Yi L <[email protected]>
> > Signed-off-by: Yi Sun <[email protected]>
> > Signed-off-by: Jacob Pan <[email protected]>
> > ---
> > v6 -> v7:
> > *) current VFIO returns allocated pasid via signed int, thus VFIO UAPI
> > can only support 31 bits pasid. If user space gives min,max which is
> > wider than 31 bits, should fail the allocation or free request.
> >
> > 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/[email protected]/
> >
> > 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 | 76
> +++++++++++++++++++++++++++++++++++++++++
> > drivers/vfio/vfio_pasid.c | 10 ++++++
> > include/linux/vfio.h | 6 ++++
> > include/uapi/linux/vfio.h | 43 +++++++++++++++++++++++
> > 5 files changed, 136 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 3c0048b..bd4b668 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 {
> > @@ -2000,6 +2001,11 @@ 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;
> > }
> > @@ -2127,6 +2133,26 @@ 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;
> > + struct ioasid_set *set;
> > +
> > + vmm = vfio_mm_get_from_task(current);
> > + if (IS_ERR(vmm)) {
> > + ret = PTR_ERR(vmm);
> > + goto out_detach;
> > + }
> > + iommu->vmm = vmm;
> > +
> > + set = vfio_mm_ioasid_set(vmm);
> > + ret = iommu_domain_set_attr(domain->domain,
> > + DOMAIN_ATTR_IOASID_SET,
> > + set);
> > + if (ret)
> > + goto out_detach;
> > + }
> > }
> >
> > /* Get aperture info */
> > @@ -2908,6 +2934,54 @@ 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;
> > +
> > + /*
> > + * Current VFIO_IOMMU_PASID_REQUEST only supports at most
> > + * 31 bits PASID. The min,max value from userspace should
> > + * not exceed 31 bits.
>
> Please describe the source of this restriction. I think it's due to
> using the ioctl return value to return the PASID, thus excluding the
> negative values, but aren't we actually restricted to pasid_bits
> exposed in the nesting_info?
yes, the description for this restriction is in the uapi/vfio.h. I
think you are right. We should restricted to the pasid_bits exposed
in the nesting_info. thanks for the spotting.
> If this is just a sanity test for the API
> then why are we defining VFIO_IOMMU_PASID_BITS in the uapi header,
> which causes conflicting information to the user... which do they
> honor?
yes, it should not be in the uapi header. will fix it.
> Should we instead verify that pasid_bits matches our API scheme
> when configuring the nested domain and then let the ioasid allocator
> reject requests outside of the range?
agreed, I think it may be checked in the attach_group phase, if pasid_bits
from iommu vendor driver are larger than 31 bits, we fail the attach.
>
> > + */
> > + if (req.range.min > req.range.max ||
> > + req.range.min > (1 << VFIO_IOMMU_PASID_BITS) ||
> > + req.range.max > (1 << VFIO_IOMMU_PASID_BITS))
>
> Off by one, >= for the bit test.
got it. thanks for spotting it.
> > + 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;
>
> Set the initial value when it's declared?
I see, will do. :-)
> > + 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)
> > {
> > @@ -2924,6 +2998,8 @@ 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 44ecdd5..0ec4660 100644
> > --- a/drivers/vfio/vfio_pasid.c
> > +++ b/drivers/vfio/vfio_pasid.c
> > @@ -60,6 +60,7 @@ 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)
> > {
> > @@ -113,6 +114,13 @@ struct vfio_mm *vfio_mm_get_from_task(struct
> task_struct *task)
> > mmput(mm);
> > return vmm;
> > }
> > +EXPORT_SYMBOL_GPL(vfio_mm_get_from_task);
> > +
> > +struct ioasid_set *vfio_mm_ioasid_set(struct vfio_mm *vmm)
> > +{
> > + return vmm->ioasid_set;
> > +}
> > +EXPORT_SYMBOL_GPL(vfio_mm_ioasid_set);
> >
> > /*
> > * Find PASID within @min and @max
> > @@ -201,6 +209,7 @@ 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)
> > @@ -217,6 +226,7 @@ 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..5c3d7a8 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 struct ioasid_set *vfio_mm_ioasid_set(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 struct ioasid_set *vfio_mm_ioasid_set(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 ff40f9e..a4bc42e 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -1172,6 +1172,49 @@ 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.
> > + *
> > + * Current interface supports at most 31 bits PASID bits as returning
> > + * PASID allocation result via signed int. PCIe spec defines 20 bits
> > + * for PASID width, so 31 bits is enough. As a result user space should
> > + * provide min, max no more than 31 bits.
>
> Perhaps this is the description I was looking for, but this still
> conflicts with what I think the user is supposed to do, which is to
> provide a range within nesting_info.pasid_bits. These seem like
> implementation details, not uapi. Thanks,
agreed, I may move this comment (after refining :-)) to the place attach_group
where we check if pasid_bits matches our API scheme, and just put a comment
"userspace should provide a range within nesting_info.pasid_bits" here.
Regards,
Yi Liu
> Alex
>
> > + * 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_BITS 31
> > +
> > +#define VFIO_IOMMU_PASID_REQUEST _IO(VFIO_TYPE, VFIO_BASE + 18)
> > +
> > /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
> >
> > /*
_______________________________________________
iommu mailing list
[email protected]
https://lists.linuxfoundation.org/mailman/listinfo/iommu
