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Date: Mon, 19 Nov 2018 09:48:55 +0100
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] SeaBIOS booting time optimization
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To: Stefano Garzarella <sgarzare@redhat.com>
Cc: seabios@seabios.org, Paolo Bonzini <pbonzini@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel@nongnu.org, Rob Bradford <robert.bradford@intel.com>, Samuel Ortiz <sameo@linux.intel.com>

  Hi,

> I'm investigating the SeaBIOS booting time, to understand if we can
> reduce the boot time in some cases (e.g. legacy hardware is not
> needed). I think this can be interesting also for NEMU developers.

> The goal is to have only one image of SeaBIOS configurable at runtime
> to reduce the boot time, avoiding unnecessary initialization.

Why at runtime?  What is bad with two images?  With a runtime option
you probably need some way to enable the "fastboot" hint for seabios,
because some optimizations (like skipping ps/2 initialization) breaks
functionality.  So it must be opt-in so you can enable it if you know
your use case is fine with that.  But "qemu -boot fast=on" isn't much
different from "qemu -bios seabios-fastboot.bin" after all ...

> Any pointers or suggestions would be helpful.

seabios could try to skip initializing hardware without bootindex with
"qemu -boot menu=off,strict=on".

mmconfig support?  I think that would reduce the number of vmexits
needed for pci initialization.

cheers,
  Gerd