[Bug 241774] FreeBSD 11.3 & 12.0 has broken SCSI & Networking on KVM/QEMU Q35 with OVMF

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=241774

--- Comment #22 from John Hartley <drum at graphica.com.au> ---
(In reply to Vincenzo Maffione from comment #21)

Hi Vincenzo,

thank you very much of for responding.

My testing has been to try to isolate where the problems lies.

The issues appears when you go from 11.2 -> 11.3 .

As the problem relates to device detection / initialisation, my initial thought
was that problem might be in PCI/PCIe code.

To test this I tried to create a custom 11.3 kernel with 11.2 PCI subsystem.

The impact of regression to 11.2 PCI was that I also had to regress netmap,
network and driver code back to 11.2 as well.

The resulting 11.3 (with 11.2 pci / networking) kernel no longer had the issue
(ie e1000, vmxnet3 & rtl8139 all working ok)

So I then rolled forward the pci code back to 11.3 .

Again testing worked with each of e1000, vmxnet3 & rtl8139 working.

So this seemed to have issue as being in netmap or drivers ...

In looking at record of code updates, the netmap related changes (refactoring
etc) and adding support for netmap in e1000 & vmxnet3 drivers all related to
MFC r339639 (which I believe was big upstream netmap alignment and
refactoring).

So right now I have not confirmed that the bug is in netmap, but it might be...

On a related front this VirtIO bug:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=236922 required changes to
both VirtIO driver and netmap.

Right now I am a bit stuck in finding the defect, as netmap and driver code is
more complex and requires deeper understand than I have. My objective was just
try to pin point where the problem was.

Having looked at this I now have a much greater appreciation of what the
dev/netmap code does and why it impacts such a large portion of network code.

On my working 11.3 / 11.2 custom kernel here is dmesg result from em0:

em0: <Intel(R) PRO/1000 Legacy Network Connection 1.1.0> port 0x9000-0x903f mem
0xc8600000-0xc861ffff irq 23 at device 1.0 on pci2
em0: Ethernet address: 52:54:00:4e:50:91
em0: netmap queues/slots: TX 1/256, RX 1/256


So it appears that netmap is enabled by default.
The only configuration I have done is set DHCP on:

# cat /etc/rc.conf
clear_tmp_enable="YES"
...
ifconfig_em0="DHCP"
local_unbound_enable="YES"
sshd_enable="YES"
# Set dumpdev to "AUTO" to enable crash dumps, "NO" to disable
dumpdev="AUTO"



Right now I have not managed to get problem isolated so specific code item...

Your advise on helping to get to the bottom of problem would be appreciated.


Cheers,

John Hartley

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