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Re: [Qemu-devel] Announcing qboot, a minimal x86 firmware for QEMU

From: Kevin O'Connor
Subject: Re: [Qemu-devel] Announcing qboot, a minimal x86 firmware for QEMU
Date: Mon, 25 May 2015 11:11:52 -0400
User-agent: Mutt/1.5.23 (2014-03-12)

On Mon, May 25, 2015 at 02:52:51PM +0200, Paolo Bonzini wrote:
> On 23/05/2015 01:23, Kevin O'Connor wrote:
> > I'm curious if you've tried profiling SeaBIOS to see where it is
> > spending unnecessary time?
> No, I really wanted to get the absolute minimum time needed to get to
> the kernel.  I announced it publicly because I think it's also instructive.
> > I wonder if a stripped down SeaBIOS could
> > obtain sufficient performance.
> It most likely could.  However, some of the features (e.g. booting
> vmlinuz from parallel flash or, in the future, from persistent memory)
> probably do not fit SeaBIOS very well.  One would have to redo them
> otherwise, for example using a DMA interface in fw_cfg.

I think adding vmlinuz and/or multiboot support to SeaBIOS would be
generally useful (and not difficult).

If a kernel was placed in memory (or memory-mapped flash) then I think
it would be reasonable to have SeaBIOS obtain its address from (an
unoptimized) fw_cfg and deploy it.


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