Hi,
In
function virPCIDeviceIsBehindSwitchLackingACS, I noticed
that(line 8):
1
if (virPCIDeviceGetParent(dev, &parent) < 0)
2
return -1;
3
if (!parent) {
4
/* if we have no parent, and this is the root bus, ACS
doesn't come
5
* into play since devices on the root bus can't P2P without
going
6
* through the root IOMMU.
7
*/
8
if (dev->address.bus == 0) {
9
return 0;
10
} else {
11
virReportError(VIR_ERR_INTERNAL_ERROR,
12
_("Failed to find parent device for
%s"),
13
dev->name);
14
return -1;
15
}
16
}
Why
we just return 0 only if device’s bus is 0?
In
my server, I can see a root bus which bus number is greater
than 0, see the
results(just
a part) after I run lspci -t:
+-[0000:80]-+-02.0-[81-83]--+-00.0
|
| \-00.1
|
+-05.0
|
+-05.1
|
+-05.2
|
\-05.4
+-[0000:7f]-+-08.0
|
+-08.2
|
+-08.3
|
+ . . .
|
\-1f.2
\-[0000:00]-+-00.0
+-01.0-[01]----00.0
+-02.0-[02]--+-00.0
| +-00.1
| +-00.2
| \-00.3
+-02.2-[03]--
+-03.0-[04-0b]----00.0-[05-0b]--+-08.0-[06-08]----00.0
| \-10.0-[09-0b]----00.0
+-05.0
+-05.1
+-05.2
+-05.4
+-11.0
+-11.4
+-16.0
+-16.1
+-1a.0
If
I assign the device 0000:81:00.0 to a VM, I get “Failed to
find parent device”.
I
think I should get no error with return value 0 just like
bus number is 0, because
bus
80 is the root bus as well in my case.
In
the <<Intel C610 Series Chipset and Intel X99 Chipset
Platform Controller Hub(PCH)>>
Datasheet,
I found that(Chapter 9.1):
For
some server platforms, it may be desirable to have multiple
PCHs in the system
Which
means some PCH’s may reside on a bus greater than 0.
So,
is this a bug?