Hi Jean,
On 2020/11/11 21:57, Jean-Philippe Brucker wrote:
Hi Baolu,
Thanks for the review. I'm only now reworking this and realized I've never
sent a reply, sorry about that.
On Wed, May 20, 2020 at 02:42:21PM +0800, Lu Baolu wrote:
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>
[...]
+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?
PAGE_RESP_FAILURE maps to PRI Response code "Response Failure" which
indicates a catastrophic error and causes the function to disable PRI.
Instead PAGE_RESP_INVALID maps to PRI Response code "Invalid request",
which tells the function that the address is invalid and there is no point
retrying this particular access.
Thanks for the explanation. I am also working on converting Intel VT-d
to use this framework (and the sva helpers). So far so good.
Best regards,
baolu
