Re: [PATCH RFC 08/11] iommu: Handle IO page faults directly

Jean-Philippe Brucker
2022-03-21T11:36:09Z

On Sun, Mar 20, 2022 at 02:40:27PM +0800, Lu Baolu wrote:
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index c0966fc9b686..4f90b71c6f6e 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -27,6 +27,8 @@
> #include <linux/cc_platform.h>
> #include <trace/events/iommu.h>
>
> +#include "iommu-sva-lib.h"
> +
> static struct kset *iommu_group_kset;
> static DEFINE_IDA(iommu_group_ida);
>
> @@ -1177,10 +1179,9 @@ int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt)
> if (!param || !evt)
> return -EINVAL;
>
> - /* we only report device fault if there is a handler registered */
> mutex_lock(&param->lock);
> fparam = param->fault_param;
> - if (!fparam || !fparam->handler) {
> + if (!fparam) {
> ret = -EINVAL;
> goto done_unlock;
> }
> @@ -1198,7 +1199,11 @@ int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt)
> mutex_unlock(&fparam->lock);
> }
>
> - ret = fparam->handler(&evt->fault, fparam->data);
> + if (fparam->handler)
> + ret = fparam->handler(&evt->fault, fparam->data);
> + else
> + ret = iommu_queue_iopf(&evt->fault, fparam->data);
> +

I like the change, but we'll need to consolidate this, because now if the
driver registers a fault handler it disables IOPF. We could instead
prevent registration if an IOPF param is present. We could also just merge
fparam->handler but eventually I'd like to make IOPF fall back to the
fault handler registered by device driver, in case of invalid page faults.
I have a couple patches for this but am still missing some bits.

Thanks,
Jean

> if (ret && evt_pending) {
> mutex_lock(&fparam->lock);
> list_del(&evt_pending->list);
> --
> 2.25.1
>