Re: [PATCH v4 12/15] iommu/vt-d: Cleanup get_valid_domain_for_dev()

From: Lu Baolu <baolu.lu@linux.intel.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: baolu.lu@linux.intel.com, kevin.tian@intel.com,
	ashok.raj@intel.com, dima@arista.com, tmurphy@arista.com,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	jacob.jun.pan@intel.com, David Woodhouse <dwmw2@infradead.org>,
	Joerg Roedel <jroedel@suse.de>
Subject: Re: [PATCH v4 12/15] iommu/vt-d: Cleanup get_valid_domain_for_dev()
Date: Tue, 6 Aug 2019 08:06:49 +0800	[thread overview]
Message-ID: <605e3cdb-35bd-45c6-73be-d3263c11def8@linux.intel.com> (raw)
In-Reply-To: <20190802105406.53cd9977@x1.home>

Hi Alex,

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