Re: [Qemu-discuss] How to resolve "Failed to mmap" error?

[A223 A223]

On Thu, Oct 6, 2016 at 9:46 AM, Alex Williamson
<address@hidden> wrote:
> On Wed, 5 Oct 2016 20:30:34 -0700
> A223 A223 <address@hidden> wrote:
>
>> On Wed, Oct 5, 2016 at 9:33 AM, Alex Williamson
>> <address@hidden> wrote:
>> > On Wed, 5 Oct 2016 02:13:21 -0700
>> > A223 A223 <address@hidden> wrote:
>> >> How can I go about tracking down the root cause of this error?
>> >
>> > This often means that the device resources are in use by another,
>> > non-pci driver.  Look in /proc/iomem and /proc/ioport to see if any
>> > drivers are claiming sub-regions on the device.  You can also turn on
>> > tracing and look for the event vfio_region_mmap_fault, which might give
>> > us more information (see docs/tracing.txt).  Also, please provide 'sudo
>> > lspci -vvvs 5:00.0' so we can see the device resources.  Thanks,
>>
>> The simpletrace output wouldn't parse for me using the python script
>> (I'll paste the trace at the end of this email), so I used the ftrace
>> backend instead (
>> https://drive.google.com/open?id=0Bwjufq6oAZMfMVpUYTUxODR0NW8 ). It's
>> quite large and I'm not sure what I'm looking for, so I didn't look at
>> it very carefully.
>
> That's not the right trace, that's like kvm trace or something.  Try:
>
> # ./configure --enable-trace-backends=log
>
> # echo vfio_region_mmap_fault > events.txt
>
> Then add to your qemu commandline "-trace events=events.txt".  You
> should get maybe a couple extra log lines per boot, not gobs of output.

Ah, got it. Here are the relevant log lines then:

address@hidden:vfio_region_mmap_fault Region 0000:05:00.0 BAR
2 mmaps[0], [20000000000 - 1ffffffffff], fault: -22
qemu-system-x86_64: -device
vfio-pci,host=05:00.0,bus=root.1,addr=00.5: Failed to mmap
0000:05:00.0 BAR 2. Performance may be slow

Thanks,

Andrew