[vfio-users] What does intel VBIOS do in SeaBIOS.bin?

Alex Williamson alex.williamson at redhat.com
Wed Oct 17 20:00:07 UTC 2018


On Wed, 17 Oct 2018 17:45:52 +0200
Laszlo Ersek <lersek at redhat.com> wrote:

> On 10/16/18 05:31, Acewind wrote:
> > In hostdev passthrough, rombar=off also works. Is seabios running without
> > any vga rom? How can it access the vga hardware?  

If the device was initialized by the host into a VGA text mode and the
vfio-pci device has VGA support enabled, then VGA access have a good
chance of hitting the device regardless of the option ROM.
 
> rombar=off makes QEMU load the PCI expansion ROM into a "genroms" style
> fw_cfg file, rather than the PCI device's ROM BAR. SeaBIOS dispatches
> the ROM from fw_cfg then. That's how I remember it anyway.
> 
> If you truly wish to prevent oprom loading for a "-device", use the
> "romfile=''" property.

In general yes, but for vfio-pci they behave the same.  There is no
default romfile specified in the PCIDeviceClass for a vfio-pci device,
so either way gets us to pci_add_option_rom() with either a NULL
romfile or a strlen zero romfile.  Thanks,

Alex




More information about the vfio-users mailing list