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

["Richard W.M. Jones" <rjones@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 1807 bytes --]

On Fri, Apr 01, 2016 at 01:07:55PM +0200, Gerd Hoffmann wrote:
> On Fr, 2016-04-01 at 11:17 +0100, Richard W.M. Jones wrote:
> > On Fri, Apr 01, 2016 at 11:18:30AM +0200, Gerd Hoffmann wrote:
> > >   Hi,
> > > 
> > > > 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?
> > > 
> > > We already build two seabios roms: one full featued and one slightly
> > > stripped down to keep it below 128k, for backward compatibility with old
> > > machine types.
> > > 
> > > Adding a third config for -kernel boot should be easy.  For that use
> > > case we can probably also turn on seabios logging to the serial console
> > > and drop sgabios.  We don't need input (no boot menu) and we also don't
> > > need to hook into int10 (no grub/ipxe using that for output).
> > 
> > SeaBIOS logging is slow (or more likely, serial output is slow).
> > And sgabios is useful for debugging.
> 
> Ah, I see.  debuglevel=1 prints too much and debuglevel=0 has no logging
> at all.  We'd need seabios log at least the version banner to serial
> even with debuglevel=0 to replace sgabios.
> 
> https://www.kraxel.org/cgit/qemu/log/?h=work/stripped-seabios
> 
> Not hooked into -kernel yet, so you have to use "-bios bios-kboot.bin".
> 
> Comments?

I think we were working on the same thing ...  Attached is my
version.

Note that you must enable at least CONFIG_MPTABLE else virtio-scsi
does not work in the guest.  I also enabled ACPI & SMBIOS & PIRTABLE.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org

[-- Attachment #2: 0001-bios-Add-fast-variant-of-SeaBIOS-for-use-with-kernel.patch --]
[-- Type: text/plain, Size: 2625 bytes --]

>From 2c9b45d9d03c05573e1dbfc35e6750b127896be6 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Fri, 1 Apr 2016 11:35:09 +0100
Subject: [PATCH] bios: Add fast variant of SeaBIOS for use with -kernel on
 x86.

This commit adds a fast variant of SeaBIOS called 'bios-fast.bin'.

It's designed to be the fastest (also the smallest, but that's not the
main aim) SeaBIOS that is just enough to boot a Linux kernel using the
-kernel option on i686 and x86_64.

This commit does not modify the -kernel option to use this.  You have
to specify it by doing something like this:

  -kernel vmlinuz -bios bios-fast.bin

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
 Makefile                 |  3 ++-
 roms/Makefile            |  4 +++-
 roms/config.seabios-fast | 12 ++++++++++++
 3 files changed, 17 insertions(+), 2 deletions(-)
 create mode 100644 roms/config.seabios-fast

diff --git a/Makefile b/Makefile
index 1d076a9..c4e939d 100644
--- a/Makefile
+++ b/Makefile
@@ -389,7 +389,8 @@ common  de-ch  es     fo  fr-ca  hu     ja  mk  nl-be      pt  sl     tr \
 bepo    cz
 
 ifdef INSTALL_BLOBS
-BLOBS=bios.bin bios-256k.bin sgabios.bin vgabios.bin vgabios-cirrus.bin \
+BLOBS=bios.bin bios-256k.bin bios-fast.bin \
+sgabios.bin vgabios.bin vgabios-cirrus.bin \
 vgabios-stdvga.bin vgabios-vmware.bin vgabios-qxl.bin vgabios-virtio.bin \
 acpi-dsdt.aml \
 ppc_rom.bin openbios-sparc32 openbios-sparc64 openbios-ppc QEMU,tcx.bin QEMU,cgthree.bin \
diff --git a/roms/Makefile b/roms/Makefile
index 7bd1252..26b0586 100644
--- a/roms/Makefile
+++ b/roms/Makefile
@@ -61,9 +61,11 @@ default:
 	@echo "  slof           -- update slof.bin"
 	@echo "  u-boot.e500    -- update u-boot.e500"
 
-bios: build-seabios-config-seabios-128k build-seabios-config-seabios-256k
+bios: build-seabios-config-seabios-128k build-seabios-config-seabios-256k \
+      build-seabios-config-seabios-fast
 	cp seabios/builds/seabios-128k/bios.bin ../pc-bios/bios.bin
 	cp seabios/builds/seabios-256k/bios.bin ../pc-bios/bios-256k.bin
+	cp seabios/builds/seabios-fast/bios.bin ../pc-bios/bios-fast.bin
 
 seavgabios: $(patsubst %,seavgabios-%,$(vgabios_variants))
 
diff --git a/roms/config.seabios-fast b/roms/config.seabios-fast
new file mode 100644
index 0000000..98a4c27
--- /dev/null
+++ b/roms/config.seabios-fast
@@ -0,0 +1,12 @@
+# The most fastest SeaBIOS that can boot Linux using -kernel.
+CONFIG_USB=n
+CONFIG_DRIVES=n
+CONFIG_KEYBOARD=n
+CONFIG_MOUSE=n
+CONFIG_WRITABLE_UPPERMEMORY=y
+CONFIG_TCGBIOS=n
+CONFIG_PIRTABLE=y
+CONFIG_MPTABLE=y
+CONFIG_SMBIOS=y
+CONFIG_ACPI=y
+CONFIG_DEBUG_LEVEL=0
-- 
2.7.4