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

From: Richard W.M. Jones
Subject: Re: [Qemu-devel] Why is SeaBIOS used with -kernel?
Date: Fri, 1 Apr 2016 09:44:56 +0100
User-agent: Mutt/1.5.20 (2009-12-10)

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_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?


Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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