Re: [PATCH 3/9] iommu: Add common code to handle IO page faults

From: Baolu Lu
Date: Tue Jul 11 2023 - 22:37:21 EST


On 2023/7/12 4:50, Jacob Pan wrote:
Hi Lu,

On Tue, 11 Jul 2023 09:06:36 +0800, Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
wrote:

The individual iommu drivers report iommu faults by calling
iommu_report_device_fault(), where a pre-registered device fault handler
is called to route the fault to another fault handler installed on the
corresponding iommu domain.

The pre-registered device fault handler is static and won't be dynamic
as the fault handler is eventually per iommu domain. Replace the device
fault handler with a static common code to avoid unnecessary code.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
drivers/iommu/iommu.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index da340f11c5f5..41328f03e8b4 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1278,6 +1278,28 @@ int iommu_unregister_device_fault_handler(struct
device *dev) }
EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
+static int iommu_handle_io_pgfault(struct device *dev,
+ struct iommu_fault *fault)
+{
+ struct iommu_domain *domain;
+
+ if (fault->type != IOMMU_FAULT_PAGE_REQ)
+ return -EINVAL;
+
+ if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID)
+ domain = iommu_get_domain_for_dev_pasid(dev,
fault->prm.pasid, 0);
+ else
+ domain = iommu_get_domain_for_dev(dev);
we don't support IOPF w/o PASID yet, right?

It's the individual driver that decides whether iopf w/o pasid is
supported or not. The iommu core doesn't need to make such assumption.


+
+ if (!domain || !domain->iopf_handler)
+ return -ENODEV;
+
+ if (domain->iopf_handler == iommu_sva_handle_iopf)
+ return iommu_queue_iopf(fault, dev);
Just wondering why have a special treatment for SVA domain. Can
iommu_queue_iopf() be used as SVA domain->iopf_handler?

Yes. I will make this change according to Kevin's suggestion in this
thread.


+
+ return domain->iopf_handler(fault, dev, domain->fault_data);
+}
+
/**
* iommu_report_device_fault() - Report fault event to device driver
* @dev: the device
@@ -1320,7 +1342,7 @@ int iommu_report_device_fault(struct device *dev,
struct iommu_fault_event *evt) mutex_unlock(&fparam->lock);
}
- ret = fparam->handler(&evt->fault, fparam->data);
+ ret = iommu_handle_io_pgfault(dev, &evt->fault);
if (ret && evt_pending) {
mutex_lock(&fparam->lock);
list_del(&evt_pending->list);


Thanks,

Jacob


Best regards,
baolu