Xen devel - Jul 2013 - Xen 4.3/AMD: setup ssss:bb:dd.f for d0 failed (-ENODEV)

While testing Xen 4.3 on my AMD testbox I noticed the following output from the
hypervisor (this has no visible effect on at least simple operation):

(XEN) setup 0000:00:18.0 for d0 failed (-19)
(XEN) setup 0000:00:18.1 for d0 failed (-19)
(XEN) setup 0000:00:18.2 for d0 failed (-19)
(XEN) setup 0000:00:18.3 for d0 failed (-19)
(XEN) setup 0000:00:18.4 for d0 failed (-19)
(XEN) setup 0000:00:19.0 for d0 failed (-19)
(XEN) setup 0000:00:19.1 for d0 failed (-19)
(XEN) setup 0000:00:19.2 for d0 failed (-19)
(XEN) setup 0000:00:19.3 for d0 failed (-19)
(XEN) setup 0000:00:19.4 for d0 failed (-19)

The PCI devices related to the output are all PCI host bridges:

00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor HyperTransport Configuration
00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor Address Map
00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor Miscellaneous Control
00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor Link Control
00:19.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor HyperTransport Configuration
00:19.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor Address Map
00:19.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor DRAM Controller
00:19.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor Miscellaneous Control
00:19.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
 Family 10h Processor Link Control

This all seems to be related to PCI passthrough setup started from
xen/drivers/passthrough/vtd/iommu.c:intel_iommu_dom0_init() or
xen/drivers/passthrough/amd/pci_amd_iommu.c:amd_iommu_dom0_init()

While the Intel code skips over bridge type entries, the AMD code has no such
exception and will fail the handler with -ENODEV when find_iommu_for_device
fails. But I am not sure one can just compare implementations here.

Would someone have more insight to decide whether skipping host bridges in
amd_iommu_setup_dom0_device would make sense? I do not see any bad effects
caused by this but it does not look good and did not happen before.

-Stefan



_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel

>>> On 22.07.13 at 14:55, Stefan Bader
<stefan.bader@canonical.com> wrote:
> While testing Xen 4.3 on my AMD testbox I noticed the following output from
> the
> hypervisor (this has no visible effect on at least simple operation):
> 
> (XEN) setup 0000:00:18.0 for d0 failed (-19)
> (XEN) setup 0000:00:18.1 for d0 failed (-19)
> (XEN) setup 0000:00:18.2 for d0 failed (-19)
> (XEN) setup 0000:00:18.3 for d0 failed (-19)
> (XEN) setup 0000:00:18.4 for d0 failed (-19)
> (XEN) setup 0000:00:19.0 for d0 failed (-19)
> (XEN) setup 0000:00:19.1 for d0 failed (-19)
> (XEN) setup 0000:00:19.2 for d0 failed (-19)
> (XEN) setup 0000:00:19.3 for d0 failed (-19)
> (XEN) setup 0000:00:19.4 for d0 failed (-19)
> 
> The PCI devices related to the output are all PCI host bridges:
> 
> 00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor HyperTransport Configuration
> 00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor Address Map
> 00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor DRAM Controller
> 00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor Miscellaneous Control
> 00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor Link Control
> 00:19.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor HyperTransport Configuration
> 00:19.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor Address Map
> 00:19.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor DRAM Controller
> 00:19.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor Miscellaneous Control
> 00:19.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>  Family 10h Processor Link Control
> 
> This all seems to be related to PCI passthrough setup started from
> xen/drivers/passthrough/vtd/iommu.c:intel_iommu_dom0_init() or
> xen/drivers/passthrough/amd/pci_amd_iommu.c:amd_iommu_dom0_init()
> 
> While the Intel code skips over bridge type entries, the AMD code has no 
> such
> exception and will fail the handler with -ENODEV when find_iommu_for_device
> fails. But I am not sure one can just compare implementations here.
> 
> Would someone have more insight to decide whether skipping host bridges in
> amd_iommu_setup_dom0_device would make sense? I do not see any bad effects
> caused by this but it does not look good and did not happen before.
Fundamentally this looks like a BIOS bug, and hence doing as you
suggest unconditionally is not an option imo. Adding code to skip
host bridges (under the assumption that they won''t initiate
transactions that might require translation by the IOMMU) may be
an option if enabled only via command line option.

In any event I''d like to hear Suravee''s opinion on this first.

Jan

On 8/5/2013 7:58 AM, Jan Beulich wrote:
>>>> On 22.07.13 at 14:55, Stefan Bader
<stefan.bader@canonical.com> wrote:
>> While testing Xen 4.3 on my AMD testbox I noticed the following output
from
>> the
>> hypervisor (this has no visible effect on at least simple operation):
>>
>> (XEN) setup 0000:00:18.0 for d0 failed (-19)
>> (XEN) setup 0000:00:18.1 for d0 failed (-19)
>> (XEN) setup 0000:00:18.2 for d0 failed (-19)
>> (XEN) setup 0000:00:18.3 for d0 failed (-19)
>> (XEN) setup 0000:00:18.4 for d0 failed (-19)
>> (XEN) setup 0000:00:19.0 for d0 failed (-19)
>> (XEN) setup 0000:00:19.1 for d0 failed (-19)
>> (XEN) setup 0000:00:19.2 for d0 failed (-19)
>> (XEN) setup 0000:00:19.3 for d0 failed (-19)
>> (XEN) setup 0000:00:19.4 for d0 failed (-19)
>>
>> The PCI devices related to the output are all PCI host bridges:
>>
>> 00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor HyperTransport Configuration
>> 00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor Address Map
>> 00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor DRAM Controller
>> 00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor Miscellaneous Control
>> 00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor Link Control
>> 00:19.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor HyperTransport Configuration
>> 00:19.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor Address Map
>> 00:19.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor DRAM Controller
>> 00:19.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor Miscellaneous Control
>> 00:19.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>   Family 10h Processor Link Control
>>
>> This all seems to be related to PCI passthrough setup started from
>> xen/drivers/passthrough/vtd/iommu.c:intel_iommu_dom0_init() or
>> xen/drivers/passthrough/amd/pci_amd_iommu.c:amd_iommu_dom0_init()
>>
>> While the Intel code skips over bridge type entries, the AMD code has
no
>> such
>> exception and will fail the handler with -ENODEV when
find_iommu_for_device
>> fails. But I am not sure one can just compare implementations here.
>>
>> Would someone have more insight to decide whether skipping host bridges
in
>> amd_iommu_setup_dom0_device would make sense? I do not see any bad
effects
>> caused by this but it does not look good and did not happen before.
> Fundamentally this looks like a BIOS bug, and hence doing as you
> suggest unconditionally is not an option imo.
Actually, I don''t think this is a BIOS bug.  I have looked through the
IVRS table
on the system that I have and it looks correct to me in the sense that it does
not list
all these processor host bridge devices for IOMMU.  As Stefan mentioned, the
current
dom0 PCI setup code scans through PCI bus does not have filter for the host
bridges which
do not need IOMMU. However, these error message should not be harmful.  Also, in
debug mode,
it clearly state that "No iommu for device 0000:00:18.0".
> Adding code to skip host bridges (under the assumption that they
won''t initiate
> transactions that might require translation by the IOMMU) may be
> an option if enabled only via command line option.
Currently, pdev_type() in driver/passthrough/pci.c only match the
PCI_CLASS_BRIDGE_PCI (0x0604)
and not the Host/PCI bridge (0x600) which I see what the devices 0:18.x, 0x19.x
are reporting in
the PCI class code structure. This might need to change?

Suravee

>>> On 06.08.13 at 04:02, Suravee Suthikulanit
<suravee.suthikulpanit@amd.com>
wrote:
> On 8/5/2013 7:58 AM, Jan Beulich wrote:
>>>>> On 22.07.13 at 14:55, Stefan Bader
<stefan.bader@canonical.com> wrote:
>>> While testing Xen 4.3 on my AMD testbox I noticed the following
output from
>>> the
>>> hypervisor (this has no visible effect on at least simple
operation):
>>>
>>> (XEN) setup 0000:00:18.0 for d0 failed (-19)
>>> (XEN) setup 0000:00:18.1 for d0 failed (-19)
>>> (XEN) setup 0000:00:18.2 for d0 failed (-19)
>>> (XEN) setup 0000:00:18.3 for d0 failed (-19)
>>> (XEN) setup 0000:00:18.4 for d0 failed (-19)
>>> (XEN) setup 0000:00:19.0 for d0 failed (-19)
>>> (XEN) setup 0000:00:19.1 for d0 failed (-19)
>>> (XEN) setup 0000:00:19.2 for d0 failed (-19)
>>> (XEN) setup 0000:00:19.3 for d0 failed (-19)
>>> (XEN) setup 0000:00:19.4 for d0 failed (-19)
>>>
>>> The PCI devices related to the output are all PCI host bridges:
>>>
>>> 00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor HyperTransport Configuration
>>> 00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor Address Map
>>> 00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor DRAM Controller
>>> 00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor Miscellaneous Control
>>> 00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor Link Control
>>> 00:19.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor HyperTransport Configuration
>>> 00:19.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor Address Map
>>> 00:19.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor DRAM Controller
>>> 00:19.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor Miscellaneous Control
>>> 00:19.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>   Family 10h Processor Link Control
>>>
>>> This all seems to be related to PCI passthrough setup started from
>>> xen/drivers/passthrough/vtd/iommu.c:intel_iommu_dom0_init() or
>>> xen/drivers/passthrough/amd/pci_amd_iommu.c:amd_iommu_dom0_init()
>>>
>>> While the Intel code skips over bridge type entries, the AMD code
has no
>>> such
>>> exception and will fail the handler with -ENODEV when
find_iommu_for_device
>>> fails. But I am not sure one can just compare implementations here.
>>>
>>> Would someone have more insight to decide whether skipping host
bridges in
>>> amd_iommu_setup_dom0_device would make sense? I do not see any bad
effects
>>> caused by this but it does not look good and did not happen before.
>> Fundamentally this looks like a BIOS bug, and hence doing as you
>> suggest unconditionally is not an option imo.
> 
> Actually, I don''t think this is a BIOS bug.  I have looked through
the IVRS
> table
> on the system that I have and it looks correct to me in the sense that it 
> does not list
> all these processor host bridge devices for IOMMU.  As Stefan mentioned,
the
> current
> dom0 PCI setup code scans through PCI bus does not have filter for the host
> bridges which
> do not need IOMMU. However, these error message should not be harmful.  
> Also, in debug mode,
> it clearly state that "No iommu for device 0000:00:18.0".
So are you saying that you also see those messages in debug mode?

If so, i.e. if they are expected to always appear, we should indeed
try to avoid issuing them, as they may cause unnecessary worries
(as is the case for Stefan here).
>> Adding code to skip host bridges (under the assumption that they
won''t
> initiate
>> transactions that might require translation by the IOMMU) may be
>> an option if enabled only via command line option.
> 
> Currently, pdev_type() in driver/passthrough/pci.c only match the 
> PCI_CLASS_BRIDGE_PCI (0x0604)
> and not the Host/PCI bridge (0x600) which I see what the devices 0:18.x, 
> 0x19.x are reporting in
> the PCI class code structure. This might need to change?
We may want to change this, but this needs to be done carefully
to not cause regressions on the VT-d side (to which host bridges
currently are the same as ordinary PCI devices/PCIe endpoints).

Jan

On 8/6/2013 1:55 AM, Jan Beulich wrote:
>>>> On 06.08.13 at 04:02, Suravee Suthikulanit
<suravee.suthikulpanit@amd.com>
> wrote:
>> On 8/5/2013 7:58 AM, Jan Beulich wrote:
>>>>>> On 22.07.13 at 14:55, Stefan Bader
<stefan.bader@canonical.com> wrote:
>>>> While testing Xen 4.3 on my AMD testbox I noticed the following
output from
>>>> the
>>>> hypervisor (this has no visible effect on at least simple
operation):
>>>>
>>>> (XEN) setup 0000:00:18.0 for d0 failed (-19)
>>>> (XEN) setup 0000:00:18.1 for d0 failed (-19)
>>>> (XEN) setup 0000:00:18.2 for d0 failed (-19)
>>>> (XEN) setup 0000:00:18.3 for d0 failed (-19)
>>>> (XEN) setup 0000:00:18.4 for d0 failed (-19)
>>>> (XEN) setup 0000:00:19.0 for d0 failed (-19)
>>>> (XEN) setup 0000:00:19.1 for d0 failed (-19)
>>>> (XEN) setup 0000:00:19.2 for d0 failed (-19)
>>>> (XEN) setup 0000:00:19.3 for d0 failed (-19)
>>>> (XEN) setup 0000:00:19.4 for d0 failed (-19)
>>>>
>>>> The PCI devices related to the output are all PCI host bridges:
>>>>
>>>> 00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor HyperTransport Configuration
>>>> 00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor Address Map
>>>> 00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor DRAM Controller
>>>> 00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor Miscellaneous Control
>>>> 00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor Link Control
>>>> 00:19.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor HyperTransport Configuration
>>>> 00:19.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor Address Map
>>>> 00:19.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor DRAM Controller
>>>> 00:19.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor Miscellaneous Control
>>>> 00:19.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>    Family 10h Processor Link Control
>>>>
>>>> This all seems to be related to PCI passthrough setup started
from
>>>> xen/drivers/passthrough/vtd/iommu.c:intel_iommu_dom0_init() or
>>>>
xen/drivers/passthrough/amd/pci_amd_iommu.c:amd_iommu_dom0_init()
>>>>
>>>> While the Intel code skips over bridge type entries, the AMD
code has no
>>>> such
>>>> exception and will fail the handler with -ENODEV when
find_iommu_for_device
>>>> fails. But I am not sure one can just compare implementations
here.
>>>>
>>>> Would someone have more insight to decide whether skipping host
bridges in
>>>> amd_iommu_setup_dom0_device would make sense? I do not see any
bad effects
>>>> caused by this but it does not look good and did not happen
before.
>>> Fundamentally this looks like a BIOS bug, and hence doing as you
>>> suggest unconditionally is not an option imo.
>> Actually, I don''t think this is a BIOS bug.  I have looked
through the IVRS
>> table
>> on the system that I have and it looks correct to me in the sense that
it
>> does not list
>> all these processor host bridge devices for IOMMU.  As Stefan
mentioned, the
>> current
>> dom0 PCI setup code scans through PCI bus does not have filter for the
host
>> bridges which
>> do not need IOMMU. However, these error message should not be harmful.
>> Also, in debug mode,
>> it clearly state that "No iommu for device 0000:00:18.0".
> So are you saying that you also see those messages in debug mode?
The default (stock unstable) is showing "(XEN) setup 0000:00:18.0 for d0
failed (-19)".
With the "amd-iommu-debug" boot options, it is also showing
"(XEN) AMD-Vi: No iommu for device 0000:00:18.0".
> If so, i.e. if they are expected to always appear, we should indeed
> try to avoid issuing them, as they may cause unnecessary worries
> (as is the case for Stefan here).
Agree
>
>>> Adding code to skip host bridges (under the assumption that they
won''t
>> initiate
>>> transactions that might require translation by the IOMMU) may be
>>> an option if enabled only via command line option.
>> Currently, pdev_type() in driver/passthrough/pci.c only match the
>> PCI_CLASS_BRIDGE_PCI (0x0604)
>> and not the Host/PCI bridge (0x600) which I see what the devices
0:18.x,
>> 0x19.x are reporting in
>> the PCI class code structure. This might need to change?
> We may want to change this, but this needs to be done carefully
> to not cause regressions on the VT-d side (to which host bridges
> currently are the same as ordinary PCI devices/PCIe endpoints).
Which class code are showing on Intel system for host bridges?

Suravee
>
> Jan
>

>>> On 06.08.13 at 16:11, Suravee Suthikulanit
<suravee.suthikulpanit@amd.com>
wrote:
> On 8/6/2013 1:55 AM, Jan Beulich wrote:
>>>>> On 06.08.13 at 04:02, Suravee Suthikulanit
<suravee.suthikulpanit@amd.com>
>> wrote:
>>> On 8/5/2013 7:58 AM, Jan Beulich wrote:
>>>>>>> On 22.07.13 at 14:55, Stefan Bader
<stefan.bader@canonical.com> wrote:
>>>>> While testing Xen 4.3 on my AMD testbox I noticed the
following output from
>>>>> the
>>>>> hypervisor (this has no visible effect on at least simple
operation):
>>>>>
>>>>> (XEN) setup 0000:00:18.0 for d0 failed (-19)
>>>>> (XEN) setup 0000:00:18.1 for d0 failed (-19)
>>>>> (XEN) setup 0000:00:18.2 for d0 failed (-19)
>>>>> (XEN) setup 0000:00:18.3 for d0 failed (-19)
>>>>> (XEN) setup 0000:00:18.4 for d0 failed (-19)
>>>>> (XEN) setup 0000:00:19.0 for d0 failed (-19)
>>>>> (XEN) setup 0000:00:19.1 for d0 failed (-19)
>>>>> (XEN) setup 0000:00:19.2 for d0 failed (-19)
>>>>> (XEN) setup 0000:00:19.3 for d0 failed (-19)
>>>>> (XEN) setup 0000:00:19.4 for d0 failed (-19)
>>>>>
>>>>> The PCI devices related to the output are all PCI host
bridges:
>>>>>
>>>>> 00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor HyperTransport Configuration
>>>>> 00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor Address Map
>>>>> 00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor DRAM Controller
>>>>> 00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor Miscellaneous Control
>>>>> 00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor Link Control
>>>>> 00:19.0 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor HyperTransport Configuration
>>>>> 00:19.1 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor Address Map
>>>>> 00:19.2 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor DRAM Controller
>>>>> 00:19.3 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor Miscellaneous Control
>>>>> 00:19.4 Host bridge: Advanced Micro Devices, Inc. [AMD]
>>>>>    Family 10h Processor Link Control
>>>>>
>>>>> This all seems to be related to PCI passthrough setup
started from
>>>>> xen/drivers/passthrough/vtd/iommu.c:intel_iommu_dom0_init()
or
>>>>>
xen/drivers/passthrough/amd/pci_amd_iommu.c:amd_iommu_dom0_init()
>>>>>
>>>>> While the Intel code skips over bridge type entries, the
AMD code has no
>>>>> such
>>>>> exception and will fail the handler with -ENODEV when
find_iommu_for_device
>>>>> fails. But I am not sure one can just compare
implementations here.
>>>>>
>>>>> Would someone have more insight to decide whether skipping
host bridges in
>>>>> amd_iommu_setup_dom0_device would make sense? I do not see
any bad effects
>>>>> caused by this but it does not look good and did not happen
before.
>>>> Fundamentally this looks like a BIOS bug, and hence doing as
you
>>>> suggest unconditionally is not an option imo.
>>> Actually, I don''t think this is a BIOS bug.  I have looked
through the IVRS
>>> table
>>> on the system that I have and it looks correct to me in the sense
that it
>>> does not list
>>> all these processor host bridge devices for IOMMU.  As Stefan
mentioned, the
>>> current
>>> dom0 PCI setup code scans through PCI bus does not have filter for
the host
>>> bridges which
>>> do not need IOMMU. However, these error message should not be
harmful.
>>> Also, in debug mode,
>>> it clearly state that "No iommu for device 0000:00:18.0".
>> So are you saying that you also see those messages in debug mode?
> 
> The default (stock unstable) is showing "(XEN) setup 0000:00:18.0 for
d0
> failed (-19)".
> With the "amd-iommu-debug" boot options, it is also showing
"(XEN) AMD-Vi: No
> iommu for device 0000:00:18.0".
And both messages are a reason for the reader to expect trouble.
>> If so, i.e. if they are expected to always appear, we should indeed
>> try to avoid issuing them, as they may cause unnecessary worries
>> (as is the case for Stefan here).
> Agree
>>
>>>> Adding code to skip host bridges (under the assumption that
they won''t
>>> initiate
>>>> transactions that might require translation by the IOMMU) may
be
>>>> an option if enabled only via command line option.
>>> Currently, pdev_type() in driver/passthrough/pci.c only match the
>>> PCI_CLASS_BRIDGE_PCI (0x0604)
>>> and not the Host/PCI bridge (0x600) which I see what the devices
0:18.x,
>>> 0x19.x are reporting in
>>> the PCI class code structure. This might need to change?
>> We may want to change this, but this needs to be done carefully
>> to not cause regressions on the VT-d side (to which host bridges
>> currently are the same as ordinary PCI devices/PCIe endpoints).
> Which class code are showing on Intel system for host bridges?
0600 of course, just like AMD''s. That''s why we need to be
careful to
not unintentionally change behavior for VT-d.

Jan