The fault->mutex serializes the fault read()/write() fops and the
iommufd_fault_auto_response_faults(), mainly for fault->response. Also, it
was conveniently used to fence the fault->deliver in poll() fop and
iommufd_fault_iopf_handler().
However, copy_from/to_user() may sleep if pagefaults are enabled. Thus,
they could take a long time to wait for user pages to swap in, blocking
iommufd_fault_iopf_handler() and its caller that is typically a shared IRQ
handler of an IOMMU driver, resulting in a potential global DOS.
Instead of reusing the mutex to protect the fault->deliver list, add a
separate spinlock, nested under the mutex, to do the job.
iommufd_fault_iopf_handler() would no longer be blocked by
copy_from/to_user().
Add a free_list in iommufd_auto_response_faults(), so the spinlock can
simply fence a fast list_for_each_entry_safe routine.
Provide two deliver list helpers for iommufd_fault_fops_read() to use:
- Fetch the first iopf_group out of the fault->deliver list
- Restore an iopf_group back to the head of the fault->deliver list
Lastly, move the mutex closer to the response in the fault structure,
and update its kdoc accordingly.
Fixes: 07838f7fd5 ("iommufd: Add iommufd fault object")
Link: https://patch.msgid.link/r/20250117192901.79491-1-nicolinc@nvidia.com
Cc: stable@vger.kernel.org
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
As fput() calls the file->f_op->release op, where fault obj and ictx are
getting released, there is no need to release these two after fput() one
more time, which would result in imbalanced refcounts:
refcount_t: decrement hit 0; leaking memory.
WARNING: CPU: 48 PID: 2369 at lib/refcount.c:31 refcount_warn_saturate+0x60/0x230
Call trace:
refcount_warn_saturate+0x60/0x230 (P)
refcount_warn_saturate+0x60/0x230 (L)
iommufd_fault_fops_release+0x9c/0xe0 [iommufd]
...
VFS: Close: file count is 0 (f_op=iommufd_fops [iommufd])
WARNING: CPU: 48 PID: 2369 at fs/open.c:1507 filp_flush+0x3c/0xf0
Call trace:
filp_flush+0x3c/0xf0 (P)
filp_flush+0x3c/0xf0 (L)
__arm64_sys_close+0x34/0x98
...
imbalanced put on file reference count
WARNING: CPU: 48 PID: 2369 at fs/file.c:74 __file_ref_put+0x100/0x138
Call trace:
__file_ref_put+0x100/0x138 (P)
__file_ref_put+0x100/0x138 (L)
__fput_sync+0x4c/0xd0
Drop those two lines to fix the warnings above.
Cc: stable@vger.kernel.org
Fixes: 07838f7fd5 ("iommufd: Add iommufd fault object")
Link: https://patch.msgid.link/r/b5651beb3a6b1adeef26fffac24607353bf67ba1.1733212723.git.nicolinc@nvidia.com
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
iommufd_fault_iopf_enable has limitation to PRI on PCI/SRIOV VFs because
the PRI might be a shared resource and current iommu subsystem is not
ready to support enabling/disabling PRI on a VF without any impact on
others.
However, we have devices that appear as PCI but are actually on the AMBA
bus. These fake PCI devices have PASID capability, support stall as well
as SRIOV, so remove the limitation for these devices.
Link: https://patch.msgid.link/r/20241107043711.116-1-zhangfei.gao@linaro.org
Co-developed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
no_llseek had been defined to NULL two years ago, in commit 868941b144
("fs: remove no_llseek")
To quote that commit,
At -rc1 we'll need do a mechanical removal of no_llseek -
git grep -l -w no_llseek | grep -v porting.rst | while read i; do
sed -i '/\<no_llseek\>/d' $i
done
would do it.
Unfortunately, that hadn't been done. Linus, could you do that now, so
that we could finally put that thing to rest? All instances are of the
form
.llseek = no_llseek,
so it's obviously safe.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The response code from user space is only allowed to be SUCCESS or
INVALID. All other values are treated by the device as a response code of
Response Failure according to PCI spec, section 10.4.2.1. This response
disables the Page Request Interface for the Function.
Add a check in iommufd_fault_fops_write() to avoid invalid response
code.
Fixes: 07838f7fd5 ("iommufd: Add iommufd fault object")
Link: https://lore.kernel.org/r/20240710083341.44617-3-baolu.lu@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
When allocating a user iommufd_hw_pagetable, the user space is allowed to
associate a fault object with the hw_pagetable by specifying the fault
object ID in the page table allocation data and setting the
IOMMU_HWPT_FAULT_ID_VALID flag bit.
On a successful return of hwpt allocation, the user can retrieve and
respond to page faults by reading and writing the file interface of the
fault object.
Once a fault object has been associated with a hwpt, the hwpt is
iopf-capable, indicated by hwpt->fault is non NULL. Attaching,
detaching, or replacing an iopf-capable hwpt to an RID or PASID will
differ from those that are not iopf-capable.
Link: https://lore.kernel.org/r/20240702063444.105814-9-baolu.lu@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Add iopf-capable hw page table attach/detach/replace helpers. The pointer
to iommufd_device is stored in the domain attachment handle, so that it
can be echo'ed back in the iopf_group.
The iopf-capable hw page tables can only be attached to devices that
support the IOMMU_DEV_FEAT_IOPF feature. On the first attachment of an
iopf-capable hw_pagetable to the device, the IOPF feature is enabled on
the device. Similarly, after the last iopf-capable hwpt is detached from
the device, the IOPF feature is disabled on the device.
The current implementation allows a replacement between iopf-capable and
non-iopf-capable hw page tables. This matches the nested translation use
case, where a parent domain is attached by default and can then be
replaced with a nested user domain with iopf support.
Link: https://lore.kernel.org/r/20240702063444.105814-8-baolu.lu@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
An iommufd fault object provides an interface for delivering I/O page
faults to user space. These objects are created and destroyed by user
space, and they can be associated with or dissociated from hardware page
table objects during page table allocation or destruction.
User space interacts with the fault object through a file interface. This
interface offers a straightforward and efficient way for user space to
handle page faults. It allows user space to read fault messages
sequentially and respond to them by writing to the same file. The file
interface supports reading messages in poll mode, so it's recommended that
user space applications use io_uring to enhance read and write efficiency.
A fault object can be associated with any iopf-capable iommufd_hw_pgtable
during the pgtable's allocation. All I/O page faults triggered by devices
when accessing the I/O addresses of an iommufd_hw_pgtable are routed
through the fault object to user space. Similarly, user space's responses
to these page faults are routed back to the iommu device driver through
the same fault object.
Link: https://lore.kernel.org/r/20240702063444.105814-7-baolu.lu@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
