Hi Jean,
On 2020/5/20 1:54, Jean-Philippe Brucker wrote:
Some systems allow devices to handle I/O Page Faults in the core mm. For
example systems implementing the PCIe PRI extension or Arm SMMU stall
model. Infrastructure for reporting these recoverable page faults was
added to the IOMMU core by commit 0c830e6b3282 ("iommu: Introduce device
fault report API"). Add a page fault handler for host SVA.
IOMMU driver can now instantiate several fault workqueues and link them
to IOPF-capable devices. Drivers can choose between a single global
workqueue, one per IOMMU device, one per low-level fault queue, one per
domain, etc.
When it receives a fault event, supposedly in an IRQ handler, the IOMMU
driver reports the fault using iommu_report_device_fault(), which calls
the registered handler. The page fault handler then calls the mm fault
handler, and reports either success or failure with iommu_page_response().
When the handler succeeded, the IOMMU retries the access.
The iopf_param pointer could be embedded into iommu_fault_param. But
putting iopf_param into the iommu_param structure allows us not to care
about ordering between calls to iopf_queue_add_device() and
iommu_register_device_fault_handler().
Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
---
v6->v7: Fix leak in iopf_queue_discard_partial()
---
drivers/iommu/Kconfig | 4 +
drivers/iommu/Makefile | 1 +
include/linux/iommu.h | 51 +++++
drivers/iommu/io-pgfault.c | 459 +++++++++++++++++++++++++++++++++++++
4 files changed, 515 insertions(+)
create mode 100644 drivers/iommu/io-pgfault.c
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index d9fa5b410015..15e9dc4e503c 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -107,6 +107,10 @@ config IOMMU_SVA
bool
select IOASID
+config IOMMU_PAGE_FAULT
+ bool
+ select IOMMU_SVA
+
config FSL_PAMU
bool "Freescale IOMMU support"
depends on PCI
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 40c800dd4e3e..bf5cb4ee8409 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -4,6 +4,7 @@ obj-$(CONFIG_IOMMU_API) += iommu-traces.o
obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
obj-$(CONFIG_IOMMU_DEBUGFS) += iommu-debugfs.o
obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
+obj-$(CONFIG_IOMMU_PAGE_FAULT) += io-pgfault.o
obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o
obj-$(CONFIG_IOMMU_IO_PGTABLE_LPAE) += io-pgtable-arm.o
[SNIP]
+
+static enum iommu_page_response_code
+iopf_handle_single(struct iopf_fault *iopf)
+{
+ vm_fault_t ret;
+ struct mm_struct *mm;
+ struct vm_area_struct *vma;
+ unsigned int access_flags = 0;
+ unsigned int fault_flags = FAULT_FLAG_REMOTE;
+ struct iommu_fault_page_request *prm = &iopf->fault.prm;
+ enum iommu_page_response_code status = IOMMU_PAGE_RESP_INVALID;
+
+ if (!(prm->flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID))
+ return status;
+
+ mm = iommu_sva_find(prm->pasid);
+ if (IS_ERR_OR_NULL(mm))
+ return status;
+
+ down_read(&mm->mmap_sem);
+
+ vma = find_extend_vma(mm, prm->addr);
+ if (!vma)
+ /* Unmapped area */
+ goto out_put_mm;
+
+ if (prm->perm & IOMMU_FAULT_PERM_READ)
+ access_flags |= VM_READ;
+
+ if (prm->perm & IOMMU_FAULT_PERM_WRITE) {
+ access_flags |= VM_WRITE;
+ fault_flags |= FAULT_FLAG_WRITE;
+ }
+
+ if (prm->perm & IOMMU_FAULT_PERM_EXEC) {
+ access_flags |= VM_EXEC;
+ fault_flags |= FAULT_FLAG_INSTRUCTION;
+ }
+
+ if (!(prm->perm & IOMMU_FAULT_PERM_PRIV))
+ fault_flags |= FAULT_FLAG_USER;
+
+ if (access_flags & ~vma->vm_flags)
+ /* Access fault */
+ goto out_put_mm;
+
+ ret = handle_mm_fault(vma, prm->addr, fault_flags);
+ status = ret & VM_FAULT_ERROR ? IOMMU_PAGE_RESP_INVALID :
Do you mind telling why it's IOMMU_PAGE_RESP_INVALID but not
IOMMU_PAGE_RESP_FAILURE?
+ IOMMU_PAGE_RESP_SUCCESS;
+
+out_put_mm:
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+
+ return status;
+}
+
+static void iopf_handle_group(struct work_struct *work)
+{
+ struct iopf_group *group;
+ struct iopf_fault *iopf, *next;
+ enum iommu_page_response_code status = IOMMU_PAGE_RESP_SUCCESS;
+
+ group = container_of(work, struct iopf_group, work);
+
+ list_for_each_entry_safe(iopf, next, &group->faults, list) {
+ /*
+ * For the moment, errors are sticky: don't handle subsequent
+ * faults in the group if there is an error.
+ */
+ if (status == IOMMU_PAGE_RESP_SUCCESS)
+ status = iopf_handle_single(iopf);
+
+ if (!(iopf->fault.prm.flags &
+ IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE))
+ kfree(iopf);
+ }
+
+ iopf_complete_group(group->dev, &group->last_fault, status);
+ kfree(group);
+}
+
+/**
+ * iommu_queue_iopf - IO Page Fault handler
+ * @evt: fault event
@fault?
+ * @cookie: struct device, passed to iommu_register_device_fault_handler.
+ *
+ * Add a fault to the device workqueue, to be handled by mm.
+ *
+ * This module doesn't handle PCI PASID Stop Marker; IOMMU drivers must discard
+ * them before reporting faults. A PASID Stop Marker (LRW = 0b100) doesn't
+ * expect a response. It may be generated when disabling a PASID (issuing a
+ * PASID stop request) by some PCI devices.
+ *
+ * The PASID stop request is issued by the device driver before unbind(). Once
+ * it completes, no page request is generated for this PASID anymore and
+ * outstanding ones have been pushed to the IOMMU (as per PCIe 4.0r1.0 - 6.20.1
+ * and 10.4.1.2 - Managing PASID TLP Prefix Usage). Some PCI devices will wait
+ * for all outstanding page requests to come back with a response before
+ * completing the PASID stop request. Others do not wait for page responses, and
+ * instead issue this Stop Marker that tells us when the PASID can be
+ * reallocated.
+ *
+ * It is safe to discard the Stop Marker because it is an optimization.
+ * a. Page requests, which are posted requests, have been flushed to the IOMMU
+ * when the stop request completes.
+ * b. We flush all fault queues on unbind() before freeing the PASID.
+ *
+ * So even though the Stop Marker might be issued by the device *after* the stop
+ * request completes, outstanding faults will have been dealt with by the time
+ * we free the PASID.
+ *
+ * Return: 0 on success and <0 on error.
+ */
+int iommu_queue_iopf(struct iommu_fault *fault, void *cookie)
+{
+ int ret;
+ struct iopf_group *group;
+ struct iopf_fault *iopf, *next;
+ struct iopf_device_param *iopf_param;
+
+ struct device *dev = cookie;
+ struct dev_iommu *param = dev->iommu;
+
+ lockdep_assert_held(¶m->lock);
+
+ if (fault->type != IOMMU_FAULT_PAGE_REQ)
+ /* Not a recoverable page fault */
+ return -EOPNOTSUPP;
+
+ /*
+ * As long as we're holding param->lock, the queue can't be unlinked
+ * from the device and therefore cannot disappear.
+ */
+ iopf_param = param->iopf_param;
+ if (!iopf_param)
+ return -ENODEV;
+
+ if (!(fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE)) {
+ iopf = kzalloc(sizeof(*iopf), GFP_KERNEL);
+ if (!iopf)
+ return -ENOMEM;
+
+ iopf->fault = *fault;
+
+ /* Non-last request of a group. Postpone until the last one */
+ list_add(&iopf->list, &iopf_param->partial);
+
+ return 0;
+ }
+
+ group = kzalloc(sizeof(*group), GFP_KERNEL);
+ if (!group) {
+ /*
+ * The caller will send a response to the hardware. But we do
+ * need to clean up before leaving, otherwise partial faults
+ * will be stuck.
+ */
+ ret = -ENOMEM;
+ goto cleanup_partial;
+ }
+
+ group->dev = dev;
+ group->last_fault.fault = *fault;
+ INIT_LIST_HEAD(&group->faults);
+ list_add(&group->last_fault.list, &group->faults);
+ INIT_WORK(&group->work, iopf_handle_group);
+
+ /* See if we have partial faults for this group */
+ list_for_each_entry_safe(iopf, next, &iopf_param->partial, list) {
+ if (iopf->fault.prm.grpid == fault->prm.grpid)
+ /* Insert *before* the last fault */
+ list_move(&iopf->list, &group->faults);
+ }
+
+ queue_work(iopf_param->queue->wq, &group->work);
+ return 0;
+
+cleanup_partial:
+ list_for_each_entry_safe(iopf, next, &iopf_param->partial, list) {
+ if (iopf->fault.prm.grpid == fault->prm.grpid) {
+ list_del(&iopf->list);
+ kfree(iopf);
+ }
+ }
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_queue_iopf);
[SNIP]
+
+
+/**
+ * iopf_queue_add_device - Add producer to the fault queue
+ * @queue: IOPF queue
+ * @dev: device to add
+ *
+ * Return: 0 on success and <0 on error.
+ */
+int iopf_queue_add_device(struct iopf_queue *queue, struct device *dev)
+{
+ int ret = -EBUSY;
+ struct iopf_device_param *iopf_param;
+ struct dev_iommu *param = dev->iommu;
+
+ if (!param)
+ return -ENODEV;
+
+ iopf_param = kzalloc(sizeof(*iopf_param), GFP_KERNEL);
+ if (!iopf_param)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&iopf_param->partial);
+ iopf_param->queue = queue; iopf_param->dev = dev;
Two lines?
+
+ mutex_lock(&queue->lock);
+ mutex_lock(¶m->lock);
+ if (!param->iopf_param) {
+ list_add(&iopf_param->queue_list, &queue->devices);
+ param->iopf_param = iopf_param;
+ ret = 0;
+ }
+ mutex_unlock(¶m->lock);
+ mutex_unlock(&queue->lock);
+
+ if (ret)
+ kfree(iopf_param);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iopf_queue_add_device);
+
[SNIP]
Best regards,
baolu
