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Re: [vfio-users] "Invalid PCI ROM header signature: expecting 0xaa55, got 0xffff" when attempting to dump PCI ROM



Just retried this morning after waking my computer up from sleep (and having previously loaded a VM from earlier) and this time, the ROM dump did succeed.

Diffing the contents of lspci from then and now, the device does appear to have changed power states, even though enable in sysfs still contains 0 and attempting to write to it still gives the same "Device or resource busy" error. The kernel logs from the wake up process also don't contain anything related to that device. iomem hasn't changed from before. Alex and Auger both seem to have guessed correctly, though the steps it took to get there aren't exactly satisfying. I remember vfio-pci having a disable D3 parameter which I'll probably be looking into later today, seeing how power states seem to be involved in the problem.

Thanks for both of your help, I'll keep posting if I find new things.
- Nicolas


On 03/11/2019 01:46 AM, Nicolas Roy-Renaud wrote:
Hey, Alex, thanks for replying.

It seems like you're right on the Mem- part.

[user OCCAM ~]$ lspci -s 07:00.0 -vvv
07:00.0 VGA compatible controller: NVIDIA Corporation GM204 [GeForce GTX 970] (rev a1) (prog-if 00 [VGA controller])
    Subsystem: ASUSTeK Computer Inc. GM204 [GeForce GTX 970]
    Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-

For comparison, here's the result from last boot after firing up and shutting down a VM using that device:

[user OCCAM ~]$ lspci -s 07:00.0 -vvv
07:00.0 VGA compatible controller: NVIDIA Corporation GM204 [GeForce GTX 970] (rev a1) (prog-if 00 [VGA controller])
    Subsystem: ASUSTeK Computer Inc. GM204 [GeForce GTX 970]
    Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-

Yet when I try enabling the device, I get this :

[root OCCAM user]# echo 1 > /sys/bus/pci/devices/0000:07:00.0/enable
bash: echo: write error: Device or resource busy

Other people have apparently had similar issues caused by other drivers claiming the ressources, and /proc/iomem was showing efifb bound to that device earlier, however neither disabling it in the kernel command line or unbinding it once the system is live have solved the issue (even though it no longer shows up in iomem). Here's PCI section from iomem with video=efifb:off. All the commands whose outputs you'll see here have been run under these conditions:

00000000-00000000 : PCI Bus 0000:00

  00000000-00000000 : PCI Bus 0000:07

    00000000-00000000 : 0000:07:00.0

    00000000-00000000 : 0000:07:00.0

  00000000-00000000 : PCI Bus 0000:01

    00000000-00000000 : 0000:01:00.0

    00000000-00000000 : 0000:01:00.0

  00000000-00000000 : PCI Bus 0000:07

    00000000-00000000 : 0000:07:00.0

    00000000-00000000 : 0000:07:00.0

    00000000-00000000 : 0000:07:00.1

  00000000-00000000 : PCI Bus 0000:01

    00000000-00000000 : 0000:01:00.0

      00000000-00000000 : nvidia

    00000000-00000000 : 0000:01:00.1

      00000000-00000000 : ICH HD audio

  00000000-00000000 : PCI Bus 0000:04

    00000000-00000000 : 0000:04:00.0

    00000000-00000000 : 0000:04:00.0

      00000000-00000000 : ahci

  00000000-00000000 : PCI Bus 0000:03

    00000000-00000000 : 0000:03:00.0

    00000000-00000000 : 0000:03:00.0

      00000000-00000000 : r8169

  00000000-00000000 : 0000:00:14.0

    00000000-00000000 : xhci-hcd

  00000000-00000000 : 0000:00:1b.0

    00000000-00000000 : ICH HD audio

  00000000-00000000 : 0000:00:1f.3

  00000000-00000000 : 0000:00:1f.2

    00000000-00000000 : ahci

  00000000-00000000 : 0000:00:1d.0

    00000000-00000000 : ehci_hcd

  00000000-00000000 : 0000:00:1a.0

    00000000-00000000 : ehci_hcd

  00000000-00000000 : 0000:00:16.0

    00000000-00000000 : mei_me

  00000000-00000000 : PCI MMCONFIG 0000 [bus 00-3f]

    00000000-00000000 : Reserved

      00000000-00000000 : pnp 00:06

00000000-00000000 : Reserved

  00000000-00000000 : IOAPIC 0

Enable reverts back to 0 after the VM using the device shuts down, and trying to write 1 in that file still yields "Device or resource busy". Also, unlike what I said earlier from the last time I looked into this, it seems doing this no longer allows you to dump the ROM after the VM has shut down, with the same error message as before.

- Nicolas


On 03/10/2019 10:09 PM, Alex Williamson wrote:
On Sun, 10 Mar 2019 18:06:37 -0400
Nicolas Roy-Renaud <nicolas roy-renaud 1 ens etsmtl ca> wrote:

I've seen a lot of people before reccomand VFIO newcomers to flash their
GPU if they couldn't get their passthrough working right before, and
since I know how potentially risky and avoidable this sort of procedure
is (since QEMU lets you just pass your own ROM to the VM to be used
instead), and while attempting to go through the steps myself
<http://vfio.blogspot.com/2014/08/does-my-graphics-card-rom-support-efi.html>
(even though I've had a working VFIO setup for years), got something
unexpected.

Attempting to dump the ROM from my guest card _/freshly /_/_after a
reboot_/ results in the following error message :

cat: '/sys/bus/pci/devices/0000:07:00.0/rom': Input/output error

Accompanied by the following like in dmesg :

[ 1734.316429] vfio-pci 0000:07:00.0: Invalid PCI ROM header signature: expecting 0xaa55, got 0xffff
If lspci for the device reports:

         Control: I/O- Mem- BusMaster- ...

(specifically Mem-), this could be the reason it's failing.  The PCI
ROM BAR is a memory region and memory decode needs to be enabled on the
device in order to get access to it.  Also if you have the device
already bound to vfio-pci, the device might be in a D3 low power state,
which could make that memory region unavailable.  You can use the
'enable' file in sysfs to fix both of these, so your sequence would
look like this:

echo 1 > /sys/bus/pci/devices/0000:07:00.0/enable
echo 1 > /sys/bus/pci/devices/0000:07:00.0/rom
cat /sys/bus/pci/devices/0000:07:00.0/rom > gpu.rom
echo 0 > /sys/bus/pci/devices/0000:07:00.0/rom
echo 0 > /sys/bus/pci/devices/0000:07:00.0/enable

Thanks,
Alex

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