[v7,4/5] iommu: Support mm PASID 1:n with sva domains
Commit Message
Each mm bound to devices gets a PASID and corresponding sva domains
allocated in iommu_sva_bind_device(), which are referenced by iommu_mm
field of the mm. The PASID is released in __mmdrop(), while a sva domain
is released when no one is using it (the reference count is decremented
in iommu_sva_unbind_device()). However, although sva domains and their
PASID are separate objects such that their own life cycles could be
handled independently, an enqcmd use case may require releasing the
PASID in releasing the mm (i.e., once a PASID is allocated for a mm, it
will be permanently used by the mm and won't be released until the end
of mm) and only allows to drop the PASID after the sva domains are
released. To this end, mmgrab() is called in iommu_sva_domain_alloc() to
increment the mm reference count and mmdrop() is invoked in
iommu_domain_free() to decrement the mm reference count.
Since the required info of PASID and sva domains is kept in struct
iommu_mm_data of a mm, use mm->iommu_mm field instead of the old pasid
field in mm struct. The sva domain list is protected by iommu_sva_lock.
Besides, this patch removes mm_pasid_init(), as with the introduced
iommu_mm structure, initializing mm pasid in mm_init() is unnecessary.
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Tina Zhang <tina.zhang@intel.com>
---
Change in v7:
- Add mm_pasid_init() back and do zeroing mm->iommu_mm pointer in
mm_pasid_init() to avoid the use-after-free/double-free problem.
Changes in v6:
- Rename iommu_sva_alloc_pasid() to iommu_alloc_mm_data().
- Hold the iommu_sva_lock before invoking iommu_alloc_mm_data().
Change in v5:
- Use smp_store_release() & READ_ONCE() in storing and loading mm's
pasid value.
Change in v4:
- Rebase to v6.6-rc1.
drivers/iommu/iommu-sva.c | 92 +++++++++++++++++++++++----------------
include/linux/iommu.h | 22 ++++++++--
2 files changed, 73 insertions(+), 41 deletions(-)
Comments
On Thu, Oct 12, 2023 at 11:01:11AM +0800, Tina Zhang wrote:
> @@ -1188,15 +1193,26 @@ static inline bool tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream
> #ifdef CONFIG_IOMMU_SVA
> static inline void mm_pasid_init(struct mm_struct *mm)
> {
> - mm->pasid = IOMMU_PASID_INVALID;
> + /*
> + * During dup_mm(), a new mm will be memcpy'd from an old one and that makes
> + * the new mm and the old one point to a same iommu_mm instance. When either
> + * one of the two mms gets released, the iommu_mm instance is freed, leaving
> + * the other mm running into a use-after-free/double-free problem. To avoid
> + * the problem, zeroing the iommu_mm pointer of a new mm is needed here.
> + */
> + mm->iommu_mm = NULL;
> }
newlines after all the }, between functions doesn't checkpatch
complain?
IMHO this hunk should be moved to the prior patch.
But it all looks good to me now
Thanks,
Jason
Hi,
> -----Original Message-----
> From: Jason Gunthorpe <jgg@ziepe.ca>
> Sent: Thursday, October 12, 2023 9:43 PM
> To: Zhang, Tina <tina.zhang@intel.com>
> Cc: Tian, Kevin <kevin.tian@intel.com>; Lu Baolu <baolu.lu@linux.intel.com>;
> Michael Shavit <mshavit@google.com>; Vasant Hegde
> <vasant.hegde@amd.com>; Nicolin Chen ^C-cc=iommu @ lists . linux . dev
> <nicolinc@nvidia.com>; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v7 4/5] iommu: Support mm PASID 1:n with sva domains
>
> On Thu, Oct 12, 2023 at 11:01:11AM +0800, Tina Zhang wrote:
>
> > @@ -1188,15 +1193,26 @@ static inline bool
> > tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream #ifdef
> > CONFIG_IOMMU_SVA static inline void mm_pasid_init(struct mm_struct
> > *mm) {
> > - mm->pasid = IOMMU_PASID_INVALID;
> > + /*
> > + * During dup_mm(), a new mm will be memcpy'd from an old one
> and that makes
> > + * the new mm and the old one point to a same iommu_mm
> instance. When either
> > + * one of the two mms gets released, the iommu_mm instance is
> freed, leaving
> > + * the other mm running into a use-after-free/double-free problem.
> To avoid
> > + * the problem, zeroing the iommu_mm pointer of a new mm is
> needed here.
> > + */
> > + mm->iommu_mm = NULL;
> > }
>
> newlines after all the }, between functions doesn't checkpatch complain?
Checked with checkpatch but didn't see any complaining.
>
> IMHO this hunk should be moved to the prior patch.
In this patch, we switch to use mm->iommu_mm. That's why the iommu_mm initialization is put in this patch.
I think I met some problem about my mailbox when I was sending this new version. It didn't cc iommu@lists.linux.dev. Should I resend this version again or reply to the patches with iommu@lists.linux.dev cc'd?
Regards,
-Tina
>
> But it all looks good to me now
>
> Thanks,
> Jason
On Fri, Oct 13, 2023 at 09:57:30AM +0000, Zhang, Tina wrote:
> Hi,
>
> > -----Original Message-----
> > From: Jason Gunthorpe <jgg@ziepe.ca>
> > Sent: Thursday, October 12, 2023 9:43 PM
> > To: Zhang, Tina <tina.zhang@intel.com>
> > Cc: Tian, Kevin <kevin.tian@intel.com>; Lu Baolu <baolu.lu@linux.intel.com>;
> > Michael Shavit <mshavit@google.com>; Vasant Hegde
> > <vasant.hegde@amd.com>; Nicolin Chen ^C-cc=iommu @ lists . linux . dev
> > <nicolinc@nvidia.com>; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH v7 4/5] iommu: Support mm PASID 1:n with sva domains
> >
> > On Thu, Oct 12, 2023 at 11:01:11AM +0800, Tina Zhang wrote:
> >
> > > @@ -1188,15 +1193,26 @@ static inline bool
> > > tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream #ifdef
> > > CONFIG_IOMMU_SVA static inline void mm_pasid_init(struct mm_struct
> > > *mm) {
> > > - mm->pasid = IOMMU_PASID_INVALID;
> > > + /*
> > > + * During dup_mm(), a new mm will be memcpy'd from an old one
> > and that makes
> > > + * the new mm and the old one point to a same iommu_mm
> > instance. When either
> > > + * one of the two mms gets released, the iommu_mm instance is
> > freed, leaving
> > > + * the other mm running into a use-after-free/double-free problem.
> > To avoid
> > > + * the problem, zeroing the iommu_mm pointer of a new mm is
> > needed here.
> > > + */
> > > + mm->iommu_mm = NULL;
> > > }
> >
> > newlines after all the }, between functions doesn't checkpatch complain?
> Checked with checkpatch but didn't see any complaining.
>
> >
> > IMHO this hunk should be moved to the prior patch.
> In this patch, we switch to use mm->iommu_mm. That's why the iommu_mm initialization is put in this patch.
>
> I think I met some problem about my mailbox when I was sending this
> new version. It didn't cc iommu@lists.linux.dev. Should I resend
> this version again or reply to the patches with
> iommu@lists.linux.dev cc'd?
Tidy the nits and resend a v8 if addresses got missed
Jason
On Fri, Oct 13, 2023 at 09:03:20PM -0300, Jason Gunthorpe wrote:
> On Fri, Oct 13, 2023 at 09:57:30AM +0000, Zhang, Tina wrote:
> > I think I met some problem about my mailbox when I was sending this
> > new version. It didn't cc iommu@lists.linux.dev. Should I resend
> > this version again or reply to the patches with
> > iommu@lists.linux.dev cc'd?
>
> Tidy the nits and resend a v8 if addresses got missed
I was actually wondering why it missed iommu list. And it likely
missed those maintainers too? Perhaps should run get_maintainer
script and add the person who's going to take the series.
Thanks
Nic
@@ -12,32 +12,42 @@
static DEFINE_MUTEX(iommu_sva_lock);
/* Allocate a PASID for the mm within range (inclusive) */
-static int iommu_sva_alloc_pasid(struct mm_struct *mm, struct device *dev)
+static struct iommu_mm_data *iommu_alloc_mm_data(struct mm_struct *mm, struct device *dev)
{
+ struct iommu_mm_data *iommu_mm;
ioasid_t pasid;
- int ret = 0;
+
+ lockdep_assert_held(&iommu_sva_lock);
if (!arch_pgtable_dma_compat(mm))
- return -EBUSY;
+ return ERR_PTR(-EBUSY);
- mutex_lock(&iommu_sva_lock);
+ iommu_mm = mm->iommu_mm;
/* Is a PASID already associated with this mm? */
- if (mm_valid_pasid(mm)) {
- if (mm->pasid >= dev->iommu->max_pasids)
- ret = -EOVERFLOW;
- goto out;
+ if (iommu_mm) {
+ if (iommu_mm->pasid >= dev->iommu->max_pasids)
+ return ERR_PTR(-EOVERFLOW);
+ return iommu_mm;
}
+ iommu_mm = kzalloc(sizeof(struct iommu_mm_data), GFP_KERNEL);
+ if (!iommu_mm)
+ return ERR_PTR(-ENOMEM);
+
pasid = iommu_alloc_global_pasid(dev);
if (pasid == IOMMU_PASID_INVALID) {
- ret = -ENOSPC;
- goto out;
+ kfree(iommu_mm);
+ return ERR_PTR(-ENOSPC);
}
- mm->pasid = pasid;
- ret = 0;
-out:
- mutex_unlock(&iommu_sva_lock);
- return ret;
+ iommu_mm->pasid = pasid;
+ INIT_LIST_HEAD(&iommu_mm->sva_domains);
+ /*
+ * Make sure the write to mm->iommu_mm is not reordered in front of
+ * initialization to iommu_mm fields. If it does, readers may see a
+ * valid iommu_mm with uninitialized values.
+ */
+ smp_store_release(&mm->iommu_mm, iommu_mm);
+ return iommu_mm;
}
/**
@@ -58,31 +68,33 @@ static int iommu_sva_alloc_pasid(struct mm_struct *mm, struct device *dev)
*/
struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
{
+ struct iommu_mm_data *iommu_mm;
struct iommu_domain *domain;
struct iommu_sva *handle;
int ret;
+ mutex_lock(&iommu_sva_lock);
+
/* Allocate mm->pasid if necessary. */
- ret = iommu_sva_alloc_pasid(mm, dev);
- if (ret)
- return ERR_PTR(ret);
+ iommu_mm = iommu_alloc_mm_data(mm, dev);
+ if (IS_ERR(iommu_mm)) {
+ ret = PTR_ERR(iommu_mm);
+ goto out_unlock;
+ }
handle = kzalloc(sizeof(*handle), GFP_KERNEL);
- if (!handle)
- return ERR_PTR(-ENOMEM);
-
- mutex_lock(&iommu_sva_lock);
- /* Search for an existing domain. */
- domain = iommu_get_domain_for_dev_pasid(dev, mm->pasid,
- IOMMU_DOMAIN_SVA);
- if (IS_ERR(domain)) {
- ret = PTR_ERR(domain);
+ if (!handle) {
+ ret = -ENOMEM;
goto out_unlock;
}
- if (domain) {
- domain->users++;
- goto out;
+ /* Search for an existing domain. */
+ list_for_each_entry(domain, &mm->iommu_mm->sva_domains, next) {
+ ret = iommu_attach_device_pasid(domain, dev, iommu_mm->pasid);
+ if (!ret) {
+ domain->users++;
+ goto out;
+ }
}
/* Allocate a new domain and set it on device pasid. */
@@ -92,23 +104,23 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
goto out_unlock;
}
- ret = iommu_attach_device_pasid(domain, dev, mm->pasid);
+ ret = iommu_attach_device_pasid(domain, dev, iommu_mm->pasid);
if (ret)
goto out_free_domain;
domain->users = 1;
+ list_add(&domain->next, &mm->iommu_mm->sva_domains);
+
out:
mutex_unlock(&iommu_sva_lock);
handle->dev = dev;
handle->domain = domain;
-
return handle;
out_free_domain:
iommu_domain_free(domain);
+ kfree(handle);
out_unlock:
mutex_unlock(&iommu_sva_lock);
- kfree(handle);
-
return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
@@ -124,12 +136,13 @@ EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
void iommu_sva_unbind_device(struct iommu_sva *handle)
{
struct iommu_domain *domain = handle->domain;
- ioasid_t pasid = domain->mm->pasid;
+ struct iommu_mm_data *iommu_mm = domain->mm->iommu_mm;
struct device *dev = handle->dev;
mutex_lock(&iommu_sva_lock);
+ iommu_detach_device_pasid(domain, dev, iommu_mm->pasid);
if (--domain->users == 0) {
- iommu_detach_device_pasid(domain, dev, pasid);
+ list_del(&domain->next);
iommu_domain_free(domain);
}
mutex_unlock(&iommu_sva_lock);
@@ -205,8 +218,11 @@ iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
void mm_pasid_drop(struct mm_struct *mm)
{
- if (likely(!mm_valid_pasid(mm)))
+ struct iommu_mm_data *iommu_mm = mm->iommu_mm;
+
+ if (!iommu_mm)
return;
- iommu_free_global_pasid(mm->pasid);
+ iommu_free_global_pasid(iommu_mm->pasid);
+ kfree(iommu_mm);
}
@@ -109,6 +109,11 @@ struct iommu_domain {
struct { /* IOMMU_DOMAIN_SVA */
struct mm_struct *mm;
int users;
+ /*
+ * Next iommu_domain in mm->iommu_mm->sva-domains list
+ * protected by iommu_sva_lock.
+ */
+ struct list_head next;
};
};
};
@@ -1188,15 +1193,26 @@ static inline bool tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream
#ifdef CONFIG_IOMMU_SVA
static inline void mm_pasid_init(struct mm_struct *mm)
{
- mm->pasid = IOMMU_PASID_INVALID;
+ /*
+ * During dup_mm(), a new mm will be memcpy'd from an old one and that makes
+ * the new mm and the old one point to a same iommu_mm instance. When either
+ * one of the two mms gets released, the iommu_mm instance is freed, leaving
+ * the other mm running into a use-after-free/double-free problem. To avoid
+ * the problem, zeroing the iommu_mm pointer of a new mm is needed here.
+ */
+ mm->iommu_mm = NULL;
}
static inline bool mm_valid_pasid(struct mm_struct *mm)
{
- return mm->pasid != IOMMU_PASID_INVALID;
+ return READ_ONCE(mm->iommu_mm);
}
static inline u32 mm_get_enqcmd_pasid(struct mm_struct *mm)
{
- return mm->pasid;
+ struct iommu_mm_data *iommu_mm = READ_ONCE(mm->iommu_mm);
+
+ if (!iommu_mm)
+ return IOMMU_PASID_INVALID;
+ return iommu_mm->pasid;
}
void mm_pasid_drop(struct mm_struct *mm);
struct iommu_sva *iommu_sva_bind_device(struct device *dev,