Commit 16c11325 authored Jul 01, 2016 by Lorenzo Pieralisi Committed by Catalin Marinas Jul 08, 2016

arm64: mm: change IOMMU notifier action to attach DMA ops



Current bus notifier in ARM64 (__iommu_attach_notifier)
attempts to attach dma_ops to a device on BUS_NOTIFY_ADD_DEVICE
action notification.

This will cause issues on ACPI based systems, where PCI devices
can be added before the IOMMUs the devices are attached to
had a chance to be probed, causing failures on attempts to
attach dma_ops in that the domain for the respective IOMMU
may not be set-up yet by the time the bus notifier is run.

Devices dma_ops do not require to be set-up till the matching
device drivers are probed. This means that instead of running
the notifier attaching dma_ops to devices (__iommu_attach_notifier)
on BUS_NOTIFY_ADD_DEVICE action, it can be run just before the
device driver is bound to the device in question (on action
BUS_NOTIFY_BIND_DRIVER) so that it is certain that its IOMMU
group and domain are set-up accordingly at the time the
notifier is triggered.

This patch changes the notifier action upon which dma_ops
are attached to devices and defer it to driver binding time,
so that IOMMU devices have a chance to be probed and to register
their bus notifiers before the dma_ops attach sequence for a
device is actually carried out.

As a result we also no longer need worry about racing with
iommu_bus_notifier(), or about retrying the queue in case devices
were added too early on DT-based systems, so clean up the notifier
itself plus the additional workaround from 722ec35f ("arm64:
dma-mapping: fix handling of devices registered before arch_initcall")

Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
[rm: get rid of other now-redundant bits]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 19a469a5

arch/arm64/mm/dma-mapping.c

+5 −17

Original line number	Diff line number	Diff line
		@@ -861,15 +861,16 @@ static int __iommu_attach_notifier(struct notifier_block *nb,
		{
		struct iommu_dma_notifier_data master, tmp;

		if (action != BUS_NOTIFY_ADD_DEVICE)
		if (action != BUS_NOTIFY_BIND_DRIVER)
		return 0;

		mutex_lock(&iommu_dma_notifier_lock);
		list_for_each_entry_safe(master, tmp, &iommu_dma_masters, list) {
		if (do_iommu_attach(master->dev, master->ops,
		master->dma_base, master->size)) {
		if (data == master->dev && do_iommu_attach(master->dev,
		master->ops, master->dma_base, master->size)) {
		list_del(&master->list);
		kfree(master);
		break;
		}
		}
		mutex_unlock(&iommu_dma_notifier_lock);
		@@ -883,17 +884,8 @@ static int __init register_iommu_dma_ops_notifier(struct bus_type *bus)

		if (!nb)
		return -ENOMEM;
		/*
		* The device must be attached to a domain before the driver probe
		* routine gets a chance to start allocating DMA buffers. However,
		* the IOMMU driver also needs a chance to configure the iommu_group
		* via its add_device callback first, so we need to make the attach
		* happen between those two points. Since the IOMMU core uses a bus
		* notifier with default priority for add_device, do the same but
		* with a lower priority to ensure the appropriate ordering.
		*/

		nb->notifier_call = __iommu_attach_notifier;
		nb->priority = -100;

		ret = bus_register_notifier(bus, nb);
		if (ret) {
		@@ -917,10 +909,6 @@ static int __init __iommu_dma_init(void)
		if (!ret)
		ret = register_iommu_dma_ops_notifier(&pci_bus_type);
		#endif

		/* handle devices queued before this arch_initcall */
		if (!ret)
		__iommu_attach_notifier(NULL, BUS_NOTIFY_ADD_DEVICE, NULL);
		return ret;
		}
		arch_initcall(__iommu_dma_init);