On 6/7/24 5:30 PM, Tian, Kevin wrote:
From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Sent: Monday, May 27, 2024 12:05 PM
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.
this message needs an update. now the device pointer is not in the
attach handle.
The iommufd_device pointer is in the attach handle provided by iommufd
in attach or replace path.
and there worths a explanation about VF in the commit msg.
@@ -376,7 +377,10 @@ int iommufd_hw_pagetable_attach(struct
iommufd_hw_pagetable *hwpt,
* attachment.
*/
if (list_empty(&idev->igroup->device_list)) {
- rc = iommu_attach_group(hwpt->domain, idev->igroup->group);
+ if (hwpt->fault)
+ rc = iommufd_fault_domain_attach_dev(hwpt, idev);
+ else
+ rc = iommu_attach_group(hwpt->domain, idev-
igroup->group);
Does it read better to have a iommufd_attach_device() wrapper with
above branches handled internally?
Yes. Will do this in the next version.
+static int iommufd_fault_iopf_enable(struct iommufd_device *idev)
+{
+ struct device *dev = idev->dev;
+ int ret;
+
+ /*
+ * Once we turn on PCI/PRI support for VF, the response failure code
+ * could not be forwarded to the hardware due to PRI being a shared
you could but just doing so is incorrect. 😊
s/could/should/
Done.
+ * resource between PF and VFs. There is no coordination for this
+ * shared capability. This waits for a vPRI reset to recover.
+ */
this may go a bit further to talk about supporting it requires an emulation
in iommufd (i.e. pause any further fault delivery until vPRI reset). It is a
future work so disable it for VF at this point.
Yes.
+void iommufd_fault_domain_detach_dev(struct iommufd_hw_pagetable
*hwpt,
+ struct iommufd_device *idev)
+{
+ struct iommufd_attach_handle *handle;
+
+ handle = iommufd_device_get_attach_handle(idev);
+ iommu_detach_group_handle(hwpt->domain, idev->igroup->group);
+ iommufd_auto_response_faults(hwpt, handle);
+ iommufd_fault_iopf_disable(idev);
+ kfree(handle);
this assumes that the detach callback of the iommu driver needs to drain
in-fly page requests so no further reference to handle or queue new req
to the deliver queue when it returns, otherwise there is a use-after-free
race or stale requests in the fault queue which auto response doesn't
cleanly handle.
iirc previous discussion reveals that only intel-iommu driver guarantees
that behavior. In any case this should be documented to avoid this being
used in a non-conforming iommu driver.
If I misunderstood, some comment why no race in this window is also
appreciated. 😊
Yes. The iommu driver needs to guarantee that there will be no iopf
request for a RID or PASID after the domain has been detached. This
implies that:
- IOMMU hardware should not put further iopf in its hardware queue if
the domain has been detached.
- Before the domain detachment is complete, the iommu driver should
flush all iopf targeting the detached domain in the hardware page
request queue.
+}
+
+static int __fault_domain_replace_dev(struct iommufd_device *idev,
+ struct iommufd_hw_pagetable *hwpt,
+ struct iommufd_hw_pagetable *old)
+{
+ struct iommufd_attach_handle *handle, *curr = NULL;
+ int ret;
+
+ if (old->fault)
+ curr = iommufd_device_get_attach_handle(idev);
+
+ if (hwpt->fault) {
+ handle = kzalloc(sizeof(*handle), GFP_KERNEL);
+ if (!handle)
+ return -ENOMEM;
+
+ handle->handle.domain = hwpt->domain;
+ handle->idev = idev;
+ ret = iommu_replace_group_handle(idev->igroup->group,
+ hwpt->domain, &handle-
handle);
+ } else {
+ ret = iommu_replace_group_handle(idev->igroup->group,
+ hwpt->domain, NULL);
+ }
+
+ if (!ret && curr) {
+ iommufd_auto_response_faults(old, curr);
+ kfree(curr);
+ }
In last version you said auto response is required only when switching
from fault-capable old to fault-incapable new. But above code doesn't
reflect that description?
What the current code does is auto-respond to all page faults targeting
the old fault-capable hwpt. I'm also okay if we decide to limit this to
flushing page faults only if the new hwpt is *not* fault-capable.
Best regards,
baolu
