Hi Alex,

On 8/3/19 12:54 AM, Alex Williamson wrote:
On Fri, 2 Aug 2019 15:17:45 +0800
Lu Baolu <baolu...@linux.intel.com> wrote:

Hi Alex,

Thanks for reporting this. I will try to find a machine with a
pcie-to-pci bridge and get this issue fixed. I will update you
later.

Further debug below...

On 8/2/19 9:30 AM, Alex Williamson wrote:
DMAR: No ATSR found
DMAR: dmar0: Using Queued invalidation
DMAR: dmar1: Using Queued invalidation
pci 0000:00:00.0: DMAR: Software identity mapping
pci 0000:00:01.0: DMAR: Software identity mapping
pci 0000:00:02.0: DMAR: Software identity mapping
pci 0000:00:16.0: DMAR: Software identity mapping
pci 0000:00:1a.0: DMAR: Software identity mapping
pci 0000:00:1b.0: DMAR: Software identity mapping
pci 0000:00:1c.0: DMAR: Software identity mapping
pci 0000:00:1c.5: DMAR: Software identity mapping
pci 0000:00:1c.6: DMAR: Software identity mapping
pci 0000:00:1c.7: DMAR: Software identity mapping
pci 0000:00:1d.0: DMAR: Software identity mapping
pci 0000:00:1f.0: DMAR: Software identity mapping
pci 0000:00:1f.2: DMAR: Software identity mapping
pci 0000:00:1f.3: DMAR: Software identity mapping
pci 0000:01:00.0: DMAR: Software identity mapping
pci 0000:01:00.1: DMAR: Software identity mapping
pci 0000:03:00.0: DMAR: Software identity mapping
pci 0000:04:00.0: DMAR: Software identity mapping
DMAR: Setting RMRR:
pci 0000:00:02.0: DMAR: Setting identity map [0xbf800000 - 0xcf9fffff]
pci 0000:00:1a.0: DMAR: Setting identity map [0xbe8d1000 - 0xbe8dffff]
pci 0000:00:1d.0: DMAR: Setting identity map [0xbe8d1000 - 0xbe8dffff]
DMAR: Prepare 0-16MiB unity mapping for LPC
pci 0000:00:1f.0: DMAR: Setting identity map [0x0 - 0xffffff]
pci 0000:00:00.0: Adding to iommu group 0
pci 0000:00:00.0: Using iommu direct mapping
pci 0000:00:01.0: Adding to iommu group 1
pci 0000:00:01.0: Using iommu direct mapping
pci 0000:00:02.0: Adding to iommu group 2
pci 0000:00:02.0: Using iommu direct mapping
pci 0000:00:16.0: Adding to iommu group 3
pci 0000:00:16.0: Using iommu direct mapping
pci 0000:00:1a.0: Adding to iommu group 4
pci 0000:00:1a.0: Using iommu direct mapping
pci 0000:00:1b.0: Adding to iommu group 5
pci 0000:00:1b.0: Using iommu direct mapping
pci 0000:00:1c.0: Adding to iommu group 6
pci 0000:00:1c.0: Using iommu direct mapping
pci 0000:00:1c.5: Adding to iommu group 7
pci 0000:00:1c.5: Using iommu direct mapping
pci 0000:00:1c.6: Adding to iommu group 8
pci 0000:00:1c.6: Using iommu direct mapping
pci 0000:00:1c.7: Adding to iommu group 9

Note that group 9 contains device 00:1c.7

pci 0000:00:1c.7: Using iommu direct mapping

I'm booted with iommu=pt, so the domain type is IOMMU_DOMAIN_PT

pci 0000:00:1d.0: Adding to iommu group 10
pci 0000:00:1d.0: Using iommu direct mapping
pci 0000:00:1f.0: Adding to iommu group 11
pci 0000:00:1f.0: Using iommu direct mapping
pci 0000:00:1f.2: Adding to iommu group 11
pci 0000:00:1f.3: Adding to iommu group 11
pci 0000:01:00.0: Adding to iommu group 1
pci 0000:01:00.1: Adding to iommu group 1
pci 0000:03:00.0: Adding to iommu group 12
pci 0000:03:00.0: Using iommu direct mapping
pci 0000:04:00.0: Adding to iommu group 13
pci 0000:04:00.0: Using iommu direct mapping
pci 0000:05:00.0: Adding to iommu group 9

05:00.0 is downstream of 00:1c.7 and in the same group.  As above, the
domain is type IOMMU_DOMAIN_IDENTITY, so we take the following branch:

         } else {
                 if (device_def_domain_type(dev) == IOMMU_DOMAIN_DMA) {

Default domain type is IOMMU_DOMAIN_DMA because of the code block in
device_def_domain_type() handling bridges to conventional PCI and
conventional PCI endpoints.

                         ret = iommu_request_dma_domain_for_dev(dev);

This fails in request_default_domain_for_dev() because there's more
than one device in the group.

                         if (ret) {
                                 dmar_domain->flags |= 
DOMAIN_FLAG_LOSE_CHILDREN;
                                 if (!get_private_domain_for_dev(dev)) {

With this commit, this now returns NULL because find_domain() does find
a domain, the same one we found before this code block.

                                         dev_warn(dev,
                                                  "Failed to get a private 
domain.\n");
                                         return -ENOMEM;
                                 }

So the key factors are that I'm booting with iommu=pt and I have a
PCIe-to-PCI bridge grouped with its parent root port.  The bridge
wants an IOMMU_DOMAIN_DMA, but the group domain is already of type
IOMMU_DOMAIN_IDENTITY.  A temporary workaround is to not use
passthrough mode, but this is a regression versus previous kernels.
Thanks,


I can reproduce this issue with a local setup. I will submit the fix and
cc it to you. Please let me know if that fix doesn't solve this problem.

Best regards,
Baolu
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