Re: amd kdump failure with iommu=nopt

[Joerg Roedel]

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 <murph...@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;
 }
 
 /*