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

[Paolo Bonzini]

On 01/04/2016 10:44, 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.
> 
> However the overhead of SeaBIOS is still down from 68ms to 18ms
> (4.0% of total boot time down to 1.1%) so it's still a big gain.
> 
> I wonder how we can make use of this in qemu and downstream distros?
> Can we have a bios-min.bin which is used with -kernel boots?

That's an interesting idea.  We can look at it for 2.7.

Paolo