Re: [PATCH v2] KVM: PPC: move iommu_add_device earlier
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From: Wei Yang <hidden>
Date: 2013-08-15 05:55:35
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lkml
Subsystem:
iommu subsystem, the rest · Maintainers:
Joerg Roedel, Will Deacon, Linus Torvalds
Alexey, On Thu, Aug 15, 2013 at 12:57:19PM +1000, Alexey Kardashevskiy wrote:
The current implementation of IOMMU on sPAPR does not use iommu_ops and therefore does not call IOMMU API's bus_set_iommu() which 1) sets iommu_ops for a bus 2) registers a bus notifier Instead, PCI devices are added to IOMMU groups from subsys_initcall_sync(tce_iommu_init) which does basically the same thing without using iommu_ops callbacks. However Freescale PAMU driver (https://lkml.org/lkml/2013/7/1/158) implements iommu_ops and when tce_iommu_init is called, every PCI device is already added to some group so there is a conflict. This patch does 2 things: 1. removes the loop in which PCI devices were added to groups and adds devices as soon as they get the iommu_table pointer assigned to them. For this, the set_iommu_table_base_and_group() function is introduced. 2. moves a bus notifier to powernv code (for hotplug) in order to avoid conflict with the notifier from the Freescale driver. iommu_add_device() and iommu_del_device() are public now.
Small suggestion, how about add a prefix like "ppc_"? Since on intel, it has intel_iommu_add_device. Maybe this could help the audience.
quoted hunk ↗ jump to hunk
Signed-off-by: Alexey Kardashevskiy <redacted> ---@@ -623,3 +623,33 @@ void __init pnv_pci_init(void)ppc_md.teardown_msi_irqs = pnv_teardown_msi_irqs; #endif } + +static int tce_iommu_bus_notifier(struct notifier_block *nb, + unsigned long action, void *data) +{ + struct device *dev = data; + + switch (action) { + case BUS_NOTIFY_ADD_DEVICE: + return iommu_add_device(dev); + case BUS_NOTIFY_DEL_DEVICE: + iommu_del_device(dev); + return 0;
Recently, I encounter a problem for device remove. In some cases, the device
will not belong to any iommu_group. For example, the DMA space is not enough
and can't allocate a TCE segment. (This happens on P7IOC. I think on P8 it
won't happen.) In this case, dev->iommu_group would be NULL and kernel crash
in iommu_group_remove_device(), since it try to reference group->notifier.
In iommu_bus_notifier(), it will check dev->iommu_group before calling the
remove_device.
if (ops->remove_device && dev->iommu_group)
So I suggest to add this check here too.
BTW, I have a patch like this, which I put the check in iommu_group_remove_device.
This could protect the kernel from do the removing without the check outside.
Author: Wei Yang [off-list ref]
Date: Wed Aug 14 04:45:06 2013 -0400
iommu: check dev->iommu_group before removing a device
In some cases, one device may not associate with any iommu_group.
For example, not enough DMA address space.
For those devices, kernel will crash when try to remove it from an iommu_group.
This patch do the check before remove it.
Signed-off-by: Wei Yang [off-list ref]
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index fbe9ca7..fe41946 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c@@ -379,6 +379,9 @@ void iommu_group_remove_device(struct device *dev) struct iommu_group *group = dev->iommu_group; struct iommu_device *tmp_device, *device = NULL; + if (!group) + return; + /* Pre-notify listeners that a device is being removed. */ blocking_notifier_call_chain(&group->notifier, IOMMU_GROUP_NOTIFY_DEL_DEVICE, dev);
I am not sure which place is better, in iommu_group_remove_device() or in the tce_iommu_bus_notifier(). I am glad to hear your suggestions. -- Richard Yang Help you, Help me