[Qemu-devel] [PATCH] don't require a disk image for network boot

[Qemu-devel] [PATCH] don't require a disk image for network boot

[andrzej zaborowski]

---------- Forwarded message ----------
From: Ferenc Wagner <wferi@niif.hu>
To: qemu-devel@nongnu.org
Date: Thu, 08 Feb 2007 18:02:23 +0100
Subject: don't require a disk image for network boot
Hi,

What do you think about the following patch?  As a side note, I'd
really prefer option roms with serial output enabled (check
CONSOLE_DUAL on rom-o-matic).  Maybe even uncheck ASK_BOOT...  Hmm,
maybe that's already done, I couldn't see... :)

Anyway, thanks for the nice work!

Regards,
Feri.
(please Cc: me, I'm not subscribed)


diff -Nru qemu-0.9.0/vl.c qemu/vl.c
--- qemu-0.9.0/vl.c     2007-02-06 00:01:54.000000000 +0100
+++ qemu/vl.c   2007-02-08 17:54:00.723622909 +0100
@@ -7017,6 +7017,7 @@
     linux_boot = (kernel_filename != NULL);

     if (!linux_boot &&
+        boot_device != 'n' &&
         hd_filename[0] == '\0' &&
         (cdrom_index >= 0 && hd_filename[cdrom_index] == '\0') &&
         fd_filename[0] == '\0')

Re: [Qemu-devel] [PATCH] don't require a disk image for network boot

[Stuart Brady]

On Tue, Feb 13, 2007 at 03:58:13PM +0100, andrzej zaborowski wrote:
> What do you think about the following patch?  As a side note, I'd
> really prefer option roms with serial output enabled (check
> CONSOLE_DUAL on rom-o-matic).  Maybe even uncheck ASK_BOOT...  Hmm,
> maybe that's already done, I couldn't see... :)

As requested, here's the diff with the correct formatting:

diff -Nru qemu-0.9.0/vl.c qemu/vl.c
--- qemu-0.9.0/vl.c     2007-02-06 00:01:54.000000000 +0100
+++ qemu/vl.c   2007-02-08 17:54:00.723622909 +0100
@@ -7017,6 +7017,7 @@
     linux_boot = (kernel_filename != NULL);
 
     if (!linux_boot &&
+        boot_device != 'n' &&
         hd_filename[0] == '\0' && 
         (cdrom_index >= 0 && hd_filename[cdrom_index] == '\0') &&
         fd_filename[0] == '\0')

Re: [Qemu-devel] [PATCH] don't require a disk image for network boot

[Thomas Petazzoni]

Hi,

Le Tue, 13 Feb 2007 15:58:13 +0100,
"andrzej zaborowski" <balrog@zabor.org> a écrit :

> Subject: don't require a disk image for network boot

BTW, is there a reason why a disk image is required when using the
-kernel option ?

In the following case: -kernel vmlinuz -append "nfsroot=blabla", we
could boot over the network, without the need for any disk image, but
Qemu wants to have a disk image. Is it mandatory ?

Thanks,

Thomas
-- 
Thomas Petazzoni - thomas.petazzoni@enix.org
http://{thomas,sos,kos}.enix.org - http://www.toulibre.org
http://www.{livret,agenda}dulibre.org

Re: [Qemu-devel] [PATCH] don't require a disk image for network boot

[Ed Swierk]

On 2/15/07, Thomas Petazzoni <thomas.petazzoni@enix.org> wrote:
> BTW, is there a reason why a disk image is required when using the
> -kernel option ?
>
> In the following case: -kernel vmlinuz -append "nfsroot=blabla", we
> could boot over the network, without the need for any disk image, but
> Qemu wants to have a disk image. Is it mandatory ?

On Linux, -hda /dev/zero works fine, so I'd say there's no reason a
disk image is necessary.

--Ed

Re: [Qemu-devel] [PATCH] don't require a disk image for network boot

[Paul Brook]

On Thursday 15 February 2007 09:17, Thomas Petazzoni wrote:
> Hi,
>
> Le Tue, 13 Feb 2007 15:58:13 +0100,
>
> "andrzej zaborowski" <balrog@zabor.org> a écrit :
> > Subject: don't require a disk image for network boot
>
> BTW, is there a reason why a disk image is required when using the
> -kernel option ?
>
> In the following case: -kernel vmlinuz -append "nfsroot=blabla", we
> could boot over the network, without the need for any disk image, but
> Qemu wants to have a disk image. Is it mandatory ?

The BIOS doesn't know about the -kernel option, so qemu replaces the first 
sector of the disk image with a dummy bootloader that jumps to the preloaded 
kernel. It can only do that if there is an image to replace.

Paul

Re: [Qemu-devel] [PATCH] don't require a disk image for network boot

[Rob Landley]

On Thursday 15 February 2007 11:27 am, Paul Brook wrote:
> On Thursday 15 February 2007 09:17, Thomas Petazzoni wrote:
> > Hi,
> >
> > Le Tue, 13 Feb 2007 15:58:13 +0100,
> >
> > "andrzej zaborowski" <balrog@zabor.org> a écrit :
> > > Subject: don't require a disk image for network boot
> >
> > BTW, is there a reason why a disk image is required when using the
> > -kernel option ?
> >
> > In the following case: -kernel vmlinuz -append "nfsroot=blabla", we
> > could boot over the network, without the need for any disk image, but
> > Qemu wants to have a disk image. Is it mandatory ?
> 
> The BIOS doesn't know about the -kernel option, so qemu replaces the first 
> sector of the disk image with a dummy bootloader that jumps to the preloaded 
> kernel. It can only do that if there is an image to replace.

Yeah, but on Linux the standard workaround is to supply -hda /dev/zero, and if 
qemu notices that it has -kernel but no hda, from a UI perspective qemu could 
easily supply the standard workaround for itself...

Rob
-- 
"Perfection is reached, not when there is no longer anything to add, but
when there is no longer anything to take away." - Antoine de Saint-Exupery