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SubjectRe: amd kdump failure with iommu=nopt
Hi Jerry,

On Wed, May 13, 2020 at 08:18:38PM -0700, Jerry Snitselaar wrote:
> We've seen kdump failures with recent kernels (5.5, 5.6, 5.7-rc1) on
> amd systems when iommu is enabled in translation mode. In the cases so
> far there has been mpt3sas involved, but I'm also seeing io page
> faults for ahci right before mpt3sas has an io page fault:

Thanks for the report!

>> It was bisected to:
>
> commit be62dbf554c5b50718a54a359372c148cd9975c7
> Author: Tom Murphy <murphyt7@tcd.ie>
> Date: Sun Sep 8 09:56:41 2019 -0700
>
> iommu/amd: Convert AMD iommu driver to the dma-iommu api

This commit also removes the deferred attach of the device to its new
domain. Does the attached diff fix the problem for you?


Joerg

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 4050569188be..40df255b6c7a 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1889,23 +1889,37 @@ void iommu_domain_free(struct iommu_domain *domain)
}
EXPORT_SYMBOL_GPL(iommu_domain_free);

-static int __iommu_attach_device(struct iommu_domain *domain,
- struct device *dev)
+static bool __iommu_is_attach_deferred(struct iommu_domain *domain,
+ struct device *dev)
{
- int ret;
- if ((domain->ops->is_attach_deferred != NULL) &&
- domain->ops->is_attach_deferred(domain, dev))
- return 0;
+ if (!domain->ops->is_attach_deferred)
+ return false;
+
+ return domain->ops->is_attach_deferred(domain, dev);
+}

+static int __iommu_attach_device_no_defer(struct iommu_domain *domain,
+ struct device *dev)
+{
if (unlikely(domain->ops->attach_dev == NULL))
return -ENODEV;

ret = domain->ops->attach_dev(domain, dev);
if (!ret)
trace_attach_device_to_domain(dev);
+
return ret;
}

+static int __iommu_attach_device(struct iommu_domain *domain,
+ struct device *dev)
+{
+ if (__iommu_is_attach_deferred(domain, dev))
+ return 0;
+
+ return __iommu_attach_device_no_defer(domain, dev);
+}
+
int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
{
struct iommu_group *group;
@@ -2023,7 +2037,12 @@ EXPORT_SYMBOL_GPL(iommu_get_domain_for_dev);
*/
struct iommu_domain *iommu_get_dma_domain(struct device *dev)
{
- return dev->iommu_group->default_domain;
+ struct iommu_domain *domain = dev->iommu_group->default_domain;
+
+ if (__iommu_is_attach_deferred(domain, dev))
+ __iommu_attach_device_no_defer(domain, dev);
+
+ return domain;
}

/*
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