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SubjectRe: [PATCH v2 03/14] iommu: Move bus setup to IOMMU device registration
From
Hi Robin,

On 2022/4/28 21:18, Robin Murphy wrote:
> Move the bus setup to iommu_device_register(). This should allow
> bus_iommu_probe() to be correctly replayed for multiple IOMMU instances,
> and leaves bus_set_iommu() as a glorified no-op to be cleaned up next.

I re-fetched the latest patches on

https://gitlab.arm.com/linux-arm/linux-rm/-/commits/iommu/bus

and rolled back the head to "iommu: Cleanup bus_set_iommu".

The test machine still hangs during boot.

I went through the code. It seems that the .probe_device for Intel IOMMU
driver can't handle the probe replay well. It always assumes that the
device has never been probed.

Best regards,
baolu

>
> At this point we can also handle cleanup better than just rolling back
> the most-recently-touched bus upon failure - which may release devices
> owned by other already-registered instances, and still leave devices on
> other buses with dangling pointers to the failed instance. Now it's easy
> to clean up the exact footprint of a given instance, no more, no less.
>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> drivers/iommu/iommu.c | 51 +++++++++++++++++++++++--------------------
> 1 file changed, 27 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 6c4621afc8cf..c89af4dc54c2 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -175,6 +175,14 @@ static int __init iommu_subsys_init(void)
> }
> subsys_initcall(iommu_subsys_init);
>
> +static int remove_iommu_group(struct device *dev, void *data)
> +{
> + if (dev->iommu && dev->iommu->iommu_dev == data)
> + iommu_release_device(dev);
> +
> + return 0;
> +}
> +
> /**
> * iommu_device_register() - Register an IOMMU hardware instance
> * @iommu: IOMMU handle for the instance
> @@ -197,12 +205,29 @@ int iommu_device_register(struct iommu_device *iommu,
> spin_lock(&iommu_device_lock);
> list_add_tail(&iommu->list, &iommu_device_list);
> spin_unlock(&iommu_device_lock);
> +
> + for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
> + struct bus_type *bus = iommu_buses[i];
> + int err;
> +
> + WARN_ON(bus->iommu_ops && bus->iommu_ops != ops);
> + bus->iommu_ops = ops;
> + err = bus_iommu_probe(bus);
> + if (err) {
> + iommu_device_unregister(iommu);
> + return err;
> + }
> + }
> +
> return 0;
> }
> EXPORT_SYMBOL_GPL(iommu_device_register);
>
> void iommu_device_unregister(struct iommu_device *iommu)
> {
> + for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++)
> + bus_for_each_dev(iommu_buses[i], NULL, iommu, remove_iommu_group);
> +
> spin_lock(&iommu_device_lock);
> list_del(&iommu->list);
> spin_unlock(&iommu_device_lock);
> @@ -1655,13 +1680,6 @@ static int probe_iommu_group(struct device *dev, void *data)
> return ret;
> }
>
> -static int remove_iommu_group(struct device *dev, void *data)
> -{
> - iommu_release_device(dev);
> -
> - return 0;
> -}
> -
> static int iommu_bus_notifier(struct notifier_block *nb,
> unsigned long action, void *data)
> {
> @@ -1884,27 +1902,12 @@ static int iommu_bus_init(struct bus_type *bus)
> */
> int bus_set_iommu(struct bus_type *bus, const struct iommu_ops *ops)
> {
> - int err;
> -
> - if (ops == NULL) {
> - bus->iommu_ops = NULL;
> - return 0;
> - }
> -
> - if (bus->iommu_ops != NULL)
> + if (bus->iommu_ops && ops && bus->iommu_ops != ops)
> return -EBUSY;
>
> bus->iommu_ops = ops;
>
> - /* Do IOMMU specific setup for this bus-type */
> - err = bus_iommu_probe(bus);
> - if (err) {
> - /* Clean up */
> - bus_for_each_dev(bus, NULL, NULL, remove_iommu_group);
> - bus->iommu_ops = NULL;
> - }
> -
> - return err;
> + return 0;
> }
> EXPORT_SYMBOL_GPL(bus_set_iommu);
>

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