Re: [Qemu-devel] Why is SeaBIOS used with -kernel?

[Kevin O'Connor]

On Fri, Apr 01, 2016 at 09:44:56AM +0100, Richard W.M. Jones wrote:
> On Fri, Apr 01, 2016 at 10:24:37AM +0200, Paolo Bonzini wrote:
> > On 01/04/2016 10:14, Richard W.M. Jones wrote:
> > > Found it: only CONFIG_MPTABLE=y was necessary.  It boots with:
> > > 
> > > # CONFIG_PIRTABLE is not set
> > > CONFIG_MPTABLE=y
> > > # CONFIG_SMBIOS is not set
> > > # CONFIG_ACPI is not set
> > 
> > If you add all three it should not give any slowdown and will provide
> > full hardware features to the kernel.  qboot does ACPI and PCI bus
> > assignment (it doesn't do SMBIOS because I got bored debugging it. :))
> 
> Enabling all 4 adds about 2ms.

CONFIG_SMBIOS and CONFIG_ACPI only control the legacy internal bios
tables.  One would disable CONFIG_FW_ROMFILE_LOAD to disable the newer
ACPI tables; there is no config option currently to disable the newer
smbios tables.

These config names are a bit misleading, so they probably should be
changed in seabios.

I didn't expect disabling the above options to do anything besides
reduce the size of the seabios binary, so I'm a bit suprised it saved
2ms.  Did you have something on your qemu command-line to avoid
generating acpi/smbios tables?

-Kevin