[RFC 1/1] board: sifive: unmatched: use zero copy for initrd

[Tom Rini]

On Tue, Jul 20, 2021 at 04:46:23PM +0300, David Abdurachmanov wrote:
> On Tue, Jul 20, 2021 at 1:06 AM Tom Rini <trini at konsulko.com> wrote:
> >
> > On Mon, Jul 19, 2021 at 11:52:09PM +0200, Heinrich Schuchardt wrote:
> > >
> > >
> > > On 19.07.21 23:38, Heinrich Schuchardt wrote:
> > > > Booting Ubuntu Impish showed the following output:
> > > >
> > > >      relocaddr   = 0x00000000fff60000
> > > >
> > > >      Loading Ramdisk to fa118000, end fffff19d ...
> > > >
> > > > The initrd is overwriting the U-Boot binary. Booting fails.
> > > >
> > > > There is no need to copy the initrd from $ramdisk_addr_r.
> > > > Set init_high = ~0UL to use zero copy.
> > > >
> > > > Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> > > > ---
> > > > Generally copying to another memory location than $ramdisk_addr_r provides
> > > > no benefit whatsoever.
> > > >
> > > > But we still should find out why the initrd relocation fails so badly.
> > > > ---
> > > >   include/configs/sifive-unmatched.h | 1 +
> > > >   1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/include/configs/sifive-unmatched.h b/include/configs/sifive-unmatched.h
> > > > index d63a5f62fb..8dcfffedbe 100644
> > > > --- a/include/configs/sifive-unmatched.h
> > > > +++ b/include/configs/sifive-unmatched.h
> > > > @@ -67,6 +67,7 @@
> > > >     "scriptaddr=0x88100000\0" \
> > > >     "pxefile_addr_r=0x88200000\0" \
> > > >     "ramdisk_addr_r=0x88300000\0" \
> > > > +   "initrd_high=0xffffffffffffffff\0" \
> > > >     "kernel_comp_addr_r=0x90000000\0" \
> > >
> > > Tom remarked that kernel_comp_addr_r is poorly chosen as it will overlap
> > > with initrd if initrd exceeds 125 MiB. Current RISC-V Linux thinks
> > > initrd should fit into the first 128 MiB of RAM but that is an
> > > unnecessary restriction in Linux.
> 
> While I don't expect this to be a major issue we should definitely fix it.
> When I originally picked the value I wasn't thinking about it and
> initrd images were small.

Yeah, honestly, I think it should be a high priority thing to fix /
document.  Distro initrds tend to not be small and these overlaps end up
being a huge problem for end users.  A good and documented example of
where to put everything relative to start of DDR so that nothing should
overlap by default makes things so much easier for everyone.

-- 
Tom
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