Re: [Qemu-devel] [PATCH] Always load PowerPC kernel to KERNEL_LOAD_ADDR

[Alexander Graf]

On 26.01.2009, at 11:22, Aurelien Jarno wrote:

> On Sun, Jan 25, 2009 at 03:22:25PM +0100, Alexander Graf wrote:
> > On 25.01.2009, at 15:19, Edgar E. Iglesias wrote:
> >
> > > On Sun, Jan 25, 2009 at 12:54:27PM +0100, Alexander Graf wrote:
> > > > Linux changed its physical address location in the elf header from
> > > > 0xc0000000 to 0 on 2.6.25, causing later kernels to fail booting
> > > > with the -kernel option.
> > > >
> > > > This patch assures that the lowest segment in the elf binary is
> > > > loaded
> > > > to KERNEL_LOAD_ADDR, which is where the firmware expects it.
> > > >
> > > > With this patch applied, I was able to successfully boot a 2.6.18  
> > > > and
> > > > a 2.6.27 Linux kernel using the -kernel option.
> > > >
> > > > Signed-off-by: Alexander Graf <address@hidden>
> > > > ---
> > > > hw/ppc_oldworld.c |    4 +++-
> > > > 1 files changed, 3 insertions(+), 1 deletions(-)
> > > >
> > > > diff --git a/hw/ppc_oldworld.c b/hw/ppc_oldworld.c
> > > > index 042a40f..f64884b 100644
> > > > --- a/hw/ppc_oldworld.c
> > > > +++ b/hw/ppc_oldworld.c
> > > > @@ -207,9 +207,11 @@ static void ppc_heathrow_init (ram_addr_t
> > > > ram_size, int vga_ram_size,
> > > >    }
> > > >
> > > >    if (linux_boot) {
> > > > +        uint64_t lowaddr = 0;
> > > >        kernel_base = KERNEL_LOAD_ADDR;
> > > >        /* now we can load the kernel */
> > > > -        kernel_size = load_elf(kernel_filename, kernel_base -
> > > > 0xc0000000ULL,
> > > > +        load_elf(kernel_filename, 0, NULL, &lowaddr, NULL);
> > > > +        kernel_size = load_elf(kernel_filename, kernel_base -
> > > > lowaddr,
> > > >                               NULL, NULL, NULL);
> > >
> > > Hello,
> > >
> > > Can't you speculatively load at kernel_base assuming it's a new
> > > kernel,
> > > then only if lowaddr indicates it was an old kernel you do the  
> > > second
> > > load to fix things up?
> >
> > Hm - so we only call load_elf once for new kernels? Sounds like a  
> > good
> > idea :-).
> >
> > > Maybe also a comment or two in the code explaining the hack.. :)
> >
> > Right, that might be nice.
>
> I have just committed a fix based on your patch and implementing  
> that. I
> also added a comment explaining the hack.

Heh - I literally started to look at the patch again about 2 seconds  
before your mail came in.

Thanks!

Alex