[RFC PATCH v2 03/15] arm64: mm: change IOMMU notifier action to attach DMA ops
From: robin.murphy@arm.com (Robin Murphy)
Date: 2016-06-17 09:27:30
Also in:
linux-acpi, linux-iommu, linux-pci, lkml
Hi Lorenzo, I think this patch makes sense even independent of the rest of the series, one nit inline notwithstanding. Marek; I'm curious as to whether this could make the workaround in 722ec35f7 obsolete as well, or are all the drivers also bound super-early in the setup you had there? On 07/06/16 14:30, Lorenzo Pieralisi wrote:
quoted hunk ↗ jump to hunk
Current bus notifier in ARM64 (__iommu_attach_notifier) attempts to attach dma_ops to a device on BUS_NOTIFY_ADD_DEVICE action notification. This causes 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. Signed-off-by: Lorenzo Pieralisi <redacted> Cc: Will Deacon <redacted> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Robin Murphy <robin.murphy@arm.com> --- arch/arm64/mm/dma-mapping.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c index c566ec8..79b0882 100644 --- a/arch/arm64/mm/dma-mapping.c +++ b/arch/arm64/mm/dma-mapping.c@@ -848,7 +848,7 @@ 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)
With this, you can also get rid of the priority setting and big fat explanatory comment in register_iommu_dma_ops_notifier(). Robin.
return 0; mutex_lock(&iommu_dma_notifier_lock);