Re: [Xen-users] OVMF Network Boot

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2015-09-09 at 12:30 +0100, James Dingwall wrote:
> Your comments have prompted me to do a little bit more digging...  In the 
> network booted Linux environment I can 
> extract the rom from the network card and can show that the qemu romfile 
> option is honoured.  What I have 
> noticed though is that the option rom is disabled when executing lspci -v:
> 
> 00:03.0 Ethernet controller: Intel Corporation 82540EM Gigabit Ethernet 
> Controller (rev 03)
>         Subsystem: Red Hat, Inc QEMU Virtual Machine
>         Physical Slot: 3
>         Flags: bus master, fast devsel, latency 0, IRQ 28
>         Memory at f1000000 (32-bit, non-prefetchable) [size=128K]
>         I/O ports at c000 [size=64]
>         Expansion ROM at f1020000 [disabled] [size=128K]
>         Kernel driver in use: e1000
> 
> Similarly in the ovmf shell pci 00 03 00 -i:
> Expansion ROM Disabled(30)

I think (although I'm far from sure) that this just indicates that the BAR
which maps the option ROM is not current enabled (i.e. there is no mapping
right now, or to look at it another way the device will not respond to
accesses to that BAR), rather than the ROM being disabled.

I would expect that to be the normal state when the ROM BAR is not in
active use, i.e. I would expect the firmware to either enable the BAR of a
NIC while using the PXE stack from the ROM but to disable it by the time it
gets to launching an OS or for the BAR to only be enabled while the
firmware is copying it out into RAM at start of day.

I could be talking out my proverbial though.

Ian.

> 
> Could this be that qemu (2.2 and 2.3 tested) does not set an appropriate bit 
> in the network card's 
> configuration?
> 
> James

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